Who can help me im in the middle of a test and i dont understand these?

Question

In the middle of a test and have answered all but.........these

Evaluate 3a - 5b + c + 2b - a for a=2, b=5, c=4.

Solve 0.31x = 2.35 + 2.92

Solve 0.18x - 11.65 = 0.41x - 9.58

4x - 3 + 2x - 2 - x = 10

Solve 8r + 4(2r - 6) = 4r - 4

Answer 1

2  is 17  you get it by adding 2.35 and 2.92 together and dividing by .31

and moving the decimal place two places to the right in both sides of the equation.

Answer 2

-7,17,-9,3 and i think the last one is 5/3 or 1 2/3, but im not sure if thats right

Answer 3

1) -5

the others i dont know

edit: i will try to solve the others

edit:

2) 17

3) -9

4) 3

5) 1.7 i think-not sure

i think most of these should be correct