Answer :

15 - w/4 = 28.

Our goal is to find the variable by itself.
First, reverse the equation to cancel itself out.
Use the Multiplication and Addition Property of Equality.

So do +15 to cancel 15 out.

Add the 15 to 28, which equals 43.

Do x4, to cancel 4 out.

43 x 4 = 172.

w will equal 172.

15 - 172/4 = 28.

First try and make w the subject of the formula which is by collecting like terms
-w/4=28-15 (15 becomes - because it has been moved or the equality sign)
-w/4=13
then you cross multiply
which will be 52 = w
therefore w= 52