2x+3y=4 5x+6y=7 ∴x=(4-3×2)×½
2x=4-3y 将x=(4-3y)½代入此式 x=-1
x=(4-3y)½ 5×(2-3/2y)+6y=7
10-15/2y+6y=7
10-3/2y=7
3/2y=3
y=2