(cx/a) + f = b
isolate the x. Note the equal sign. What you do to one side, you do to the other. Do the opposite of PEMDAS.
First, subtract f from both sides
(xc/a) + f (-f) = b (-f)
xc/a = b - f
Next, multiply a to both sides
(xc/a)a = (b-f)a
Distribute a to all terms within the parenthesis
xc = ab - a(f)
Finally, to isolate the x, divide c to both sides
(xc)/c = (ab - a(f))/c
x = (ab - a(f))/c
x = (ab - a(f))/c is your answer
hope this helps
