Solve for x. y = 1/3 (x + w)

Step 1: get rid of the 1/3 by multiplying both sides by 3

3 • y = 3 • 1/3(x+w)

3y = x + w

Step 2: get the x by itself by subtracting away the w

3y - w = x + w - w

3y - w = x

You’ve got your answer.