Question 64679
Find a : 
2c/a - b = m/x
2c/a = b+(m/x)
Get a lcd on the right side:
2c/a = (bx+m)/x
Invert both sides to get:
a/2c = x/(bx+m)
Multiply both sides by 2c to ge:
a= 2cx/(bx+m)
Cheers,
Stan H.