The answer is going to be 3(2a+5)
Step-by-step explanation:
6(a+b) = 6a +30 (it is not equivalent to 6a+15)
You have to multiply what’s in the brackets by 6
3(2a+5) = 6a+15 ( it is equivalent )
3 (3a+12) = 9a+36 (not equivalent)
6(a+12) = 6a+12 (not equivalent)
I hope this helps:))