how do you work out 5x-2y=4
3x+y=9
by "work out" do you mean solve ?
double the second and add to the first
5x-2y=4
6x+2y=18
11x = 22
x = 2
sub into original 2nd
3(2) + y = 9
y = 9-6
y = 3
3x+y=9
double the second and add to the first
5x-2y=4
6x+2y=18
11x = 22
x = 2
sub into original 2nd
3(2) + y = 9
y = 9-6
y = 3