數学十萬火急!15分(誰先進來就是最佳回答!)

y = x+1..........(1)
y = 2x+3..........(2)
Put (2) into (1).
x + 1 = 2x + 3
1 - 3 = x
x = -2..........(3)
Put (3) into (1)
y = -2 + 1
y = -1
x = 3y+8..........(1)
x+6y+10 = 0..........(2)
Put (1) into (2).
3y + 8 + 6y + 10 = 0
9y + 18 = 0
y = -18 / 9
y = -2..........(3)
Put (3) into (1).
x = 3(-2) + 8
x = 2
x+y = 7..........(1)
5x = 2y..........(2)
(1) : x = 7 - y..........(3)
Put (3) into (2).
5(7 - y) = 2y
35 - 5y = 2y
35 = 7y
y = 5..........(4)
Put (4) into (1)
x + 5 = 7
x = 2
3x+y = 5..........(1)
2x+y = 8..........(2)
(1) - (2) :
x = -3..........(3)
Put (3) into (1)
3(-3) + y = 5
-9 + y = 5
y = 14