determine the resulting equation if one variable is solved in terms of the other varaiable in one equation and substitute this variable in the other equation.
1.) 4x+y=6
x-2y=15
2.) 2x+y=10
4x+2y=5
#1
The first equation says y=6-4x. So, use that in the second equation and you have
x-2(6-4x) = 15
Do #2 in like wise. Or, you can say that
2x = 10-y, so since 4x = 2(2x),
2(10-y)+2y = 5