How can i solve 3x+2y=-9 and 2x+y=-7 using substitution?

Ok so isolate the y in the second equation.
3x+2y=-9
y=-2x-7
now you know what y has to equal so input it wherever there is a y
3x+2(-2x-7)=-9
try to solve that, if you still need help comment and ill give u the answer

You must find a common number between 3 and 2 which both have the variable x. Since the common number is 6, you multiply the first whole line by 2 . The second kind by three. Then you get 6x+4y= -18, and the second line is 6x+3y=-21. You want to get rid of x, so 6x - 6x=0. Subtract the 4y and 3y which equals one. -18-21, which equals -39. So y equals -39. Multiply -39 by the y in any two equations and drop the y. The you will have for example 2x-39=-7. Then it equals 2x= -7+39. Then 2x=32. Then divide 2 by both sides. Next it is x=16. So your answer is (16, -39)