The sum of real numbers x and y is 21. Their differnce is 15. What is the value of xy?

Y + - Y=0. 2X=34 Then divide both sides by the number next to "X." X=17 Then substitute X=17 into X+Y=21. Then you get 17 + Y=21. Y=21-17=4 Next check your answers by substituting into each equation above to see if both work and are true. 17+4=21

21=21

17-4=13

13=13