any help is GREAT!

1. The grass in a meadow grew equally think and fast. 1 cow and 1 goat can eat it up in 90 weeks, 1 cow 2 goats can do it in 60 weeks. 2 cows and 1 goat can di it in 45 weeks. How many weeks would it take 2 cows and 2 goats to crop the grass of the whole meadow?

2.Tom and Jerry left their houses simultaneously to visit each other. Walking at UNIFORM speeds, they passed each other at a point 5 kilometers from Toms home without noticing. When they reached their respective destinations and found nobody home they turned around to go back, this time meeting each other at a point 3 km from Jerrys home. What was the ratio between the speed of Tom to that of Jerry?

Thanks for your help. if you could explain your answers that would be awesome!