John is a quarterback. This year, he completed 350 passes, which is 70 percent of all the passes he's attempted this year.
How many passes has John attempted this year?

So we're given the information that 350 is 70% of "x".

So let's make "x" the total amount of attempted passes.

We can re-write 70% like this: 70/100.

This means that 70/100 * x = 350.

Solve:

70/100x = 350.

Multiply 10 on both sides to get normal number:

70/100x * 10 = 350 * 10.

700/100x = 3500

7x = 3500

Divide by 7:

7x/7 = 3500/7

x = 500

they would have to work 32 hours.