Simplify:

8 (v+w) - 7 (v+2w)

First you need to distribute. when you do this you get (8v+8w) - (7v+14w) then you get like terms together, but don't forget that everything in (7v+14w) is negative. when you group like terms together you get (8v-7v) + (8w-14w) simplify and you get v-6w

The answer is v-6w ...