incorporate the shoes and socks method. We must do the opposite of what is being done. If we are adding X, we will subtract X on both sides leaving you with 8.7=7-x. We want X on one side of the equation so now we take the 8.7 and subtract on both sides giving 7-x-8.7. we must add X on both sides so we can have a X on one side thus X= 7-8.7. we can ordinary subtract and will give us -1.7.
