In 15 minutes lena can finish 2 math homework problems. how many math problems can she finish in 75 minutes?

Set up a proportion.
(x is the amount of problems she can do in 75 mins)



Now, to find 'x', we need to have it on its own, so we multiply by 75 on both sides.

 × 

The answer is 10, as  multiplied by 75 is 10.

Yo no me sé esa mala mia