Solving Equations Using the Addition Principle of Equality

Can you find the error in the following problem?

5² + (4 - 8) = x + 15

25 + 4 = x + 15

29 = x + 15

29 + (-15) =  x + 15 + (-15)

14 = x + 0

14 = x

Practice Solving Simple Equations Using the Addition Property of Equality

It is important to practice the addition property of equality.  See below and solve five simple equations using the addition property of equality.

Practice Problem #1
x - 11 = 41

Practice Problem #2
x - 17 = -35

Practice Problem #3
84 = 40 + x

Practice Problem #4
45 = -15 + x

Practice Problem #5
-21 = -52 + x


Answers:

Practice Problem #1
x - 11 = 41
x - 11 + 11 = 41 + 11
x + 0 = 52
x = 52

check

52 - 11 = 41
41 = 41

Practice Problem #2
x - 17 = -35
x - 17 + 17 = -35 + 17
x + 0 = -18
x = -18

check

-18 - 17 = -35
-35 = -35

Practice Problem #3
84 = 40 + x
84 + ( - 40) = 40 + (-40) + x
44 =  0 + x
44 = x

check
84 = 40 + 44
84 = 84

Practice Problem #4
45 = -15 + x
45 + 15 = -15 + 15 + x
60 = 0 + x
60 = x

check
45 = -15 + 60
45 =  45


Practice Problem #5
-21 = -52 + x
-21 + 52 = -52 + 52 + x
31 = 0 + x
31 = x

check
-21 = -52 + 31
-21 = -21