Question

Can you answer these? I don't understand this part either. Thanks

Answer 1

$9x+10=12x-11\\ 3x=21\\ x=7\\\\ 3(x-8)=5x+7\\ 3x-24=5x+7\\ 2x=-31\\ x=-\frac{31}{2}$

Answer 2

$9x+10=12x-11$
We put 12x on the left side and 10 on right side
$9x-12x=-11-10$
Now we add x and free numbers 
$-3x=-21$
And our result is:
$x=7$

$3(x-8)=5x+7$
$3x-24=5x+7$
$3x-5x=7+24$
$-2x=31$
$x=- \frac{31}{2}$