Hey, can anybody help me with some GRE questions that I couldn’t solve?

In how many different ways can 3 identical green shirts and 3 identical red shirts be distributed among 6 children such that each child receives a shirt?
(The options given are  20, 40, 216, 720, 729) 
If x > 0 which of the following expressions are equal to 3.6% of [pmath]{5x}/12[/pmath]?
We have to indicate all such expressions. The options given are 
 3 percent of 20 x
 x percent of [pmath]3/2[/pmath]
 3x percent of 0.2
 0.05 percent of 3 x
 [pmath]{3x}/200[/pmath]
 A driver completed the first 20 miles of a 40mile trip at an average speed of 50 miles per hour and the second 20 miles at an average speed of xx miles per hour. The average speed for the entire 40mile trip was 60 miles per hour. (Assume that the driver did not make any stops during the 40mile trip.)
Quantity A > x  60
Quantity B > 10
The options given are 
a) quantity A is greater
b) quantity B is greater
c) the two quantities are equal
d) the relationship cannot be determined from the information given.
Will really appreciate the help
Thanks