Question

-3 (u+3)+4u, what is the solution to this problem?

Answer 1

Use the distributive property to get rid of the parentheses:
-3(u+3)+4u=0
-3u-9+4u=0
Simplify to get answer by isolating the variables:
-3u-9+4u=0
-3u+4u=9
u=9
The solution would be 9, u=9

Answer 2

After simplifying, you should get u-9. Or if you want what u equals. Then I think you answer will be u=9