Solve for a. 9a - 2b = c + 4a

You move the + 4a to the left side of the equal sign and that becomes a negative

9a-2-4a=c

You move - 2 to the right side of the equal sign and that becomes a positive

9a-4a=c+2

Combine like terms

5a=c+2

Divide by 5 from each side

a = (c+2) / 5

A=25b+15c that is the answer