12: x = 2y Does 3x = 1x+4y? Yes.
13: x = 3y Does 2x + 3y = 3x + y? No.
14: 4; 2; 8
15: 2x+y=x+y+2z is equal to x=2z. Yes, because both sides of the second have y, which cancelm and x=2z.
16: 2x+y=x+y+2z is equal to x=2z. No, because the star and leaf cancel, and one side has two more circles than the other.