Question

Vera is using her phone. It's battery life is down to 1/2, and it drains another 1/8 every hour. How many hours will her battery last?

Answer 1

Four hours

In case you want to see how it's done:
1/2= 50%
1/8=12.5%

So you could multiply a small number to 12.5% or you could subtract 50% by 12.5% however many times.