Ok for this one you have to solve for b and show work

b= --6

So you multiply both sides by 6
6*5/6(12-5b)=35*6

Which would turn out to be

5(12-5b)= 210

Then divide both sides by 5
and you would get
5(12-5b)/5= 210/5

And you would get 
12-5b=4

Then subtract 12 from both sides
12-5b-12= 42-12 which is
-5b=30

now divide both sides by 5 and you would get

-6

9.8? i'm not really sure