2)
3x + y = 9 is equivalent to -15x - 5y = -45 by multiplying both sides by -5
-15x - 5y = -45
+ 4x + 5y = 23
-11x + 0y = -22
-11x = -22
x = 2
3(2) + y = 9
6 + y = 9
y = 3
4)
2x + y = 17 is equivalent to -6x - 3y = -51 by multiplying both sides by -3
4x + 3y = 37
+ (-6x - 3y = -51)
-2x + 0y = -14
-2x = -14
x = 7
4(7) + 3y = 37
28 + 3y = 37
3y = 9
y = 3
6)
x + 2y = 18 is equivalent to -10x - 20y = -180 by multiplying both sides by -10
10x - 3y = 19
+ (-10x - 20y = -180)
0x - 23y = -161
-23y = -161
y = 7
10x - 3(7) = 19
10x - 21 = 19
10x = 40
x = 4
I hope this helped ^_^