x-4y = 12 ----> equation (1)
x-6y = 15 ----> equation (2)
in equation (1)
x = 12 + 4y
now we putting the value of x in the second equation
12 + 4y -6y = 15
12 -2y = 15
-2y = 15-12
-2y = 3
y = -³/₂
now we substitute the value of y in equation (1)
x = 12 + 4y
x = 12 + 4(-³/₂)
x = 12 + (-6)
x = 12-6
x = 6
so
x= 6
and
y = -³/₂