1) 13m - 4z = -6
2) 7m + 8z = 78
multiply eq(1) by 2, add eqs (1) and (2):
26m - 8z = -12
7m + 8z = 78
_______________
33m = 66
m = 66/33 = 2
Using eq(2):
7(2) + 8z = 78
8z = 64
z = 64/8 = 8
Check using eq(1):
13(2) -4(8) = -6
26 - 32 = -6
-6 = -6
m = 2, z = 8
1) -5x + 25y = -105
2) 4x - 8y = 48
eq(2):
4x = 8y + 48
x = 2y + 12
substitute into eq(1):
-5(2y + 12) + 25y = -105
-10y - 60 + 25y = -105
15y = -45
y = -45/15 = -3
using eq(2):
x = 2(-3) + 12
x = 6
check using eq(1):
-5(6) + 25(-3) = -105
-30 + (-75) = -105
-105 = -105
x = 6, y = -3