20x= 28-8y
-8x=-56-8y
You could solve this by substitution (solving for one variable, x or y, in one equation, then substituting it into the other equation), or elimination. I'll use elimination. In elimination, you can multiple one equation by a value so that, when you add the two equations, one of the variables is cancelled out by the other equation.
(-8x = -56 - 8y) • -1
8x= 56 + 8y
20x = 28 - 8y
+ 8x = 56 + 8y
= 28x = 84 + 0y, or just 28x = 84, since 0 • y = 0.
Divide both sides by 28 to get x alone.
x = 3. Now we have one of our variables. Plug in x=3 to one of the equations to find y. I'll use 20x = 28 - 8y.
20(3) = 28 - 8y
60 = 28 - 8y
Subtract 28 from both sides. You're trying to get y alone.
32 = -8y
Divide both sides by -8.
-4 = y, or y = -4.
The answer is ( 3, -4 ). Hope this helps.