19x + rx = -37x + w
Add 37x on both sides
19x + rx + 37x = w
Factor out the x
x(19 + r + 37) = w
You can simplify this to:
x(56 + r) = w
Divide (56 + r) on both sides to get x by itself
x = [tex]\frac{w}{56 + r}[/tex]