solve for x and y: 15x- 18- 2y= -3y+ y, 10x+ 7y+ 20= 4x+ 2
We'll work both equations to get the x and y terms on the left,
and any constant value on the right.
15x - 18 - 2y= -3y + y
15x - 2y + 3y - y = 18
15x = 18
x = 18/15
x = 6/5
Now, we'll begin solving the second equation, and
substitute the value of x when get to an optimal place.
10x + 7y + 20 = 4x + 2
10x - 4x + 7y = 2 - 20
6x + 7y = -18
6 * (6/5) + 7y = -18
36/5 + 7y = -18
7y = -18 - 36/5
7y = -90/5 - 36/5
7y = -126/5
y = (-126/5) * 1/7
y = -18/5