Solve the equation

3 (-a-3) - 2 (3a+3) = -78

We are given this equation:

3 (-a-3) - 2 (3a+3) = -78

We will use distributive property here:

a (b+c) = a*b + a*c

-3a-9 - 6a-6=-78

combining like terms

-9a - 15 = -78

we add 15 to both sides

-9a - 15 + 15 = - 78+15

-9a = -63

dividing both sides by - 9

a=7

Given equation is 3 (-a-3) - 2 (3a+3) = -78

we can start by distributing numbers which are outside parenthesis

3 (-a-3) - 2 (3a+3) = -78

-3a-9-6a-6=-78

combine like terms

-9a-15=-78

-9a=-78+15

-9a=-63

a=-63/-9

a=7

Hence final answer is a=7.