Sarah and Kayla both solved the problem below. Who solved it correctly? Identify the mistake for the person who solved it incorrectly.
Sarah
Kayla
5x - 15 - 3x = 10 - (-3x + 20)
5x - 15 - 3x = 10 -(-3x + 20)
2x - 15 = 10 + 3x - 20
2x - 15 = 10 + 3x – 20
2x - 15 = -10 + 3x
2x - 15 -10 + 3x
-3x
- 3x
+3x
+ 3x
- 1x - 15 = -10
5x - 15 = -10
+ 15
+15
+15
+15
- 1x = 5
5x = 5
x = -5
X = 1
What property did they use during that step
to solve it correctly?