3(x + 7) -20 = 5x + 7

A really food answer.

but the final answer should have the x first.

x=-3

3x+21-20=5x+7                   Distribute the three to the contents of the parenthesis

3x+1=5x+7                          Go ahead and combine the 21 and -20

1=2x+7                                Subtract 3x from 5x

-6=2x                                  Subtract 7

-3=x                                     Divide by 2