Question 103920
X+Y=42 OR X=42-Y
X+2Y=57 NOW SUBSTITUTE (42-Y) FOR X & SOLVE FOR Y
(42-Y)+2Y=57
42-Y+2Y=57
Y=57-42
Y=15 ANSWER.
X=42-15
X=27 ANSWER.
PROOF
27+2*15=57
27+30=57
57=57