x+200y=20000 ……①
x+100y=15000 ……②
则②式 - ①式,得
(X+200Y) - (X+100Y) = 20000 - 15000
即
100Y = 5000
解得Y = 5000/100 = 50
将Y的值代入 ②式得
X + 100×50 = 15000
即X + 5000 = 15000
解得X = 15000 - 5000 = 10000
综上
X = 10000
Y = 50