I have a few problems that I need help with

Code:
[#9]

solve the system of equations
2x + (2/3)y = -8
1/2x - (1/3)y = 1
Code:
[#11]

Solve a system of equations to find the two numbers described.
The sum of two numbers is 17 and their difference is 29.
Code:
[#12]

The sum of a number and twice a greater number is 8. The sum of the greater number and twice the lesser number is -6.
Code:
[#16]

A boat travels 60 miles downstream in the same time it takes to go 36 miles upstream. The speed of the boat in still water is 15 mph greater than the speed of the current. Find the speed of the current.
Code:
[#36]

The geometric mean of a number and 3 is 9. Find the number: use  g = squareroot(ab)
Code:
[#50]

Al's flower garden measures 25 feet by 35 feet. He has enough crushed stone to cover 325 square feet. If he uses the stone to build a path around his garden, what is the maximum possible width of the path?
thanks in advance,

Dimava