
Anthony P. answered 03/13/13
Experienced tutor in earth sciences and basic math to trigonometry
(1) 7y = x + 2
(2) 4x - 8y = 12
To solve this system, let's choose a variable from on of the equations to solve for (it doesn't matter which equation or which variable, so let's make it easy). I'll choose to solve for x in eqn 1.
x = 7y - 2
Now substitute for x in eqn 2
4x - 8y = 12
4(7y - 2) - 8y = 12
Notice that now we have an equation that's only in terms of one variable, y. Solve for y.
28y - 8 - 8y = 12
20y = 20
y = 1
Now that we have a value for y, substitute into any equation to find x (I'll use x = 7y - 2 since it was already solved for x)
x = 7y - 2
x = 7(1) - 2 = 5
So the point of intersection of these two lines is (5 , 1)