Ok so u want to know how to find out the value of a variable its simple here is an example how. x - y = 30 while 15 = y. Now make it x - 15 = 30, we need to solve for x now so here is how we going to do it. Add both 30 and 15 to get your answer (which is to solve for x) and 30 + 15 = 45 so now 45 - 15 = 30 will be correct and true. All u had to do was add the one of the numbers to the result and u could get your answer.