"A trip of 720 km is travelled by car. On the return trip, the speed is increased by 10 km/h. The total time spewnt travelling was 17 h. Find the speed each way."

The answer is 80 km/h and 90 km/h, but I have no idea how to get there. In other words, I can't come up with the right equation to start things off.

Thanks in advance,

Sunlis