數學~易做(5點)!!!!

1)
2x + 3y = 8 ....(1)
3x - 5y = 69 ...(2) (1)*5 + (2)*3 :10x + 9x = 8*5 + 69*3
19x = 247
x = 132(13) + 3y = 8
3y = - 18
y = - 6
2) 4x + 3y = 10 ....(1)
x - y = 1/6 ........(2)(1) + (2)*3 :4x + 3x = 10 + 3/6
7x = 21/2
x = 3/24(3/2) + 3y = 10
3y = 4
y = 4/3
3)3x + 8y = 19 .....(1)
10y - 7x = -30 ...(2)(1)*7 + (2)*3 :56y + 30y = 19*7 - 30*3
86y = 43
y = 23x + 8*2 = 19
3x = 3
x = 1
4) 9x - y = 2y + 4x = 229x - y = 22 .....(1)
4x + 2y = 22 ..(2)(1)*2 + (2) :18x + 4x = 44 + 22
22x = 66
x = 34*3 + 2y = 22
2y = 10
y = 5