Kisha and Rae are asked to solve −5x − 14 = 2x + 7. Identify where one of them made an error.
Kisha

−5x − 14 = 2x + 7
−5x − 14 − 2x = 2x + 7 − 2x
−7x − 14 = 7
−7x − 14 + 14 = 7 + 14
−7x = 21
Negative 7x over negative 7 equals 21 over negative 7
x = − 3

rae
−5x − 14 = 2x + 7
−5x − 14 + 5x = 2x + 7 + 5x
−14 = 7x + 7
−14 + 7 = 7x + 7 + 7
−7 = 7x
negative 7 over 7 equals 7x over 7
x = − 1

Question

Kisha and Rae are asked to solve −5x − 14 = 2x + 7. Identify where one of them made an error.
Kisha

−5x − 14 = 2x + 7
−5x − 14 − 2x = 2x + 7 − 2x
−7x − 14 = 7
−7x − 14 + 14 = 7 + 14
−7x = 21
Negative 7x over negative 7 equals 21 over negative 7
x = − 3


rae
−5x − 14 = 2x + 7
−5x − 14 + 5x = 2x + 7 + 5x
−14 = 7x + 7
−14 + 7 = 7x + 7 + 7
−7 = 7x
negative 7 over 7 equals 7x over 7
x = − 1

campbell_st · Answer

rae made the error... 

-14 + 7 = 7x + 7 + 7

should be 

-14 - 7 = 7x + 7 - 7

then you can go and show the answer is -3

anonymous · Answer

@campbell_st not an answer choice

anonymous · Answer

Rae made the error when she added 7

 Rae made the error when she added 5x

 Kisha made the error when she subtracted 2x

 Kisha made the error when she divided by −7

campbell_st · Answer

wow... I think the 1st answer choice matched what I posted...