Just plug in the value for 'x=-3/2' into '-3(x+2)+5x=-9' and see if you get identity:

-3((-3/2)+2)+5(-3/2)=-9

9/2 - 6 - 15/2 = -9

-6 + (9-15/2) = - 9

- 6 - 6/2 = - 9

- 6 - 3 = - 9 

-9 = -9