1. Since one is cycling 2x faster than the other, they will meet at 60mi from one side of one starting point and 30mi from the other side of starting point. So one travels 15m/h and the other travels 30m/h

Average speed is (15+30)/2 = 22.5m/h

2. 6L of 120g/L brine has 720g of brine in it.

So 720g / ? = 200g/L

720g / 200g/L = 3.6L

6L - 3.6L = 2.4L needs to be boiled off

3. $7.50 * 35 = $262.50

She has earned $262.50 for her non-overtime hours.

Extra profit = $352.50 - $262.5 = $90.00

One and a half times over the original profit = $11.25 an hour

$90.00 / $11.25 = 8 overtime hours worked