What is this equation? w+13.2=10.4

If your looking for the answer its w = - 2.8

In order to solve for W you have to isolate it. To do this you have to move the 13.2 over to the other side of the equal sign. When you move it over it becomes the opposite of the original number. SO ... a + 13.2 will now become a - 13.2. Which leaves you with:

w = 10.4 - 13.2

When you do the simple subtraction you will end up with your answer:

w = - 2.8