Question 170750
X+Y=20 OR X=20-Y
X^2-Y^2=120
(20-Y)^2-Y^2=120
400-40Y+Y^2=120
-40Y=120-400
-40Y=-280
Y=-280/-40
Y=7 ans.
X+7=20
X=20-7
X=13 ans.
Proof:
13^2-7^2=120
169-49=120
120=120