Number 11. I'm not sure any help?

2x+7=16
Katherine divided wrong. She shouldn't have divided by 2 because 7 isn't a multiple of 2; x+7≠16:2.

She should have proceed like that:
2x+7=16|-7
2x=16-7
2x=9
x=9:2
x=4,5

a).  When Katherine was dividing the equation by 2, she handled the ' 2x '
correctly, and she handled the '16' correctly, but she forgot to divide the '7' by 2.

b).  Here's what she should have done.  I think this would be easier:

                                         2x + 7  =  16

Subtract  7  from each side:    2x  =  9

Divide each side by  2 :            x  =  4.5