Question

Find the error and explain why:

1. 9x+2=x+5
9x+2=6
9x=4
x=4/9

2. 3(x-4)+5=12
3x+4+5=12
3x+9=12
3x=3
x=1

Answer 1

1) 9x + 2 = x + 5 ---> 9x + 2 = 6

subtracted X from one side but not the other

2) 3(x-4) + 5 = 12 ---> 3x + 4 + 5 = 12

didn't distribute correctly: 3(x-4)

multiplied the X by 3 but not the -4