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Lecture Comments (4)

2 answers

Last reply by: Arpana Duggal
Sat Jul 14, 2012 2:51 PM

Post by James Sommers on January 26, 2012

Dear Ms. Fung,

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Thanks,
James

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Post by RAFAEL MENDIVES on June 12, 2011

In the last example she said he born in 1762, the correct answer is 1756

Solving Addition Equations

  • The objective in solving equations is to isolate the variable, to get it alone.
  • Inverse operations are operations that undo each other. Addition is the inverse operation of Subtraction. Multiplication is the opposite operation of Division.
  • The Subtraction Property of Equality says that if you subtract the same value from each side of an equation, the two sides remain equal.
  • You can use subtraction of an equation to undo addition. This will isolate the variable and show you its value. For example: x + 4 = 9. Subtract 4 from both sides and that will undo the addition next to the variable x. You will then have x = 5.

Solving Addition Equations

32 + x = 35. Solve for x.
  • 32 + x − 32 = 35 − 32
x = 3
x + 90 = 104. Solve for x.
  • x + 90 − 90 = 104 − 90
x = 14
− 2 + x + 5 = 32. Solve for x.
  • x + 3 = 32
  • x + 3 − 3 = 32 − 3
x = 29
57 = x + 2. Solve for x.
  • 57 − 2 = x + 2 − 2
55 = x
43 − a = 21 + b. a = 11. Solve for b.
  • 43 − 11 = 21 + b
  • 432 = 21 + b
  • 32 − 21 = 21 + b − 21
11 = b
21 − x = 9 + y. x = 4. Solve for y.
  • 21 − 4 = 9 + y
  • 17 = 9 + y
  • 17 − 9 = 9 + y − 9
8 = y
Orange juice used to cost $ 3.20. Due to inflation, the price of orange juice is now $ 3.79. How much more expensive is orange juice now?
  • Let j = the difference in price.
  • $ 3.20 + j = $ 3.79
  • $ 3.20 + j − $ 3.20 = $ 3.79 − $ 3.20
j = $ 0.59
Carlos bought a laptop for $ 975 and sold it online for $ 1100. How much profit is Carlos making?
  • Let P = profit
  • $ 975 + P = $ 1100
  • P = $ 1100 − $ 975
P = $ 125
Eric is 25 years old in 2012. In what year was Eric born?
  • Let y = Eric's birthyear
  • y + 25 = 2012
  • y = 2012 − 25
y = 1987
After walking for 75 feet, Michelle is now 125 feet away from her school. How far away was Michelle from school when she started walking?
  • Let w = distance, in feet, between the house and Michelle when she started walking.
  • 4x + 75 = 125
  • x = 125 − 75
  • x = 50
50 feet

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

Answer

Solving Addition Equations

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • What You'll Learn and Why 0:05
    • Topics Overview
  • Vocabulary 0:18
    • Equation
    • Isolate
    • Inverse Operations
  • Subtraction Property of Equality 1:59
    • Arithmetic
    • Algebraic
  • Inverse Operations 3:32
    • Example: 38 + x = 42
    • Using Substitution to Check Answer
  • Inverse Operations 5:19
    • Example: y + 7.3 = 9.1
    • Using Substitution to Check Answer
  • Draw a Model 6:26
    • Weight Gain
  • Draw a Model 8:20
    • Mountain Climber
  • Examples by Writing Equations 10:25
    • Calculating Profit: Sweat Shirt
  • Examples by Writing Equations 11:37
    • Calculating Profit: Car Dealer
  • Extra Example 1: Inverse Operation 14:21
  • Extra Example 2: Inverse Operation 15:37
  • Extra Example 3: Real Estate 17:23
  • Extra Example 4: Birth Date 20:06