Question 655628
1/x + 1/w = 1/y

Find the LCM which is xwy

{(wy + xy = xw)/xwy} 
Since you have an equation over the LCM, you can disregard the LCM

wy + xy = xw

Collect like terms
wy - xw = -xy

Factor out w
w(y-x) = -xy

Divide both sides by (y-x)
w = -xy/(y-x)