Answer:

Step-by-step explanation:
Recall that
.
Therefore,
.
840=2 times 2 times 2 times 3 times 5 times 7
It’s 0.5 xxxxxxxxxxxxxxxxxccc
First factor out the 2:
x^2 - y^2 = 36
x^2 - y^2 can be factored into (x+y)(y-y) so:
(x + y)(x - y) = 36
plug in your value:
18 (x-y) = 36 and you should be able to take it from there