help guys. i forgot how to do this, i forgot

1. Two, cyclist, 90 mi apart, start riding toward each other at the same time. One cycles is twice as fast as the other. If they meet 2h later, at what average speed is each cyclist traveling?

2. A pot contains 6L of brine at a concentration of 120g/L. How much of the water should be boiled off to increase the concentration of 200 g/L?

3. Helen earns $7.50 an hour at her job, but if she works more than 35 hours in a week she paid 1 1/2 (one and one half) times her regular salary for the overtime hours worked. One week her gross pay was $ 352.50. How many overtime hours did she work that week?

thanks for helping!