equation

6(x+1) = 6*(x+1)

3xy=3*x*y

If there is an operator missing it will be an invisable  multiply sign   

Is it 30? Or 13?

last sum im doin.........

we'll solve this by putting 3 on c's place

=3(3+7)

now multiply 3 by 3 and 7 by 3

= 9 + 21

= 30 ANSWER

if you still dont understand then dont ask me...

Yay I was right... in a way, cause I didnt know if it was 30 or 13.

yeah....you were not sure if it was a hill or a mountain