Explanation:
You can solve systems of equations using either substitution or elimination. For these problems, I recommend elimination. I'll do the first one as an example.
-3x + 16y = 9
-4x + 8y = 12
Multiply the second equation by -2.
8x − 16y = -24
Add to the first equation (notice the y's cancel out).
(-3x + 16y) + (8x − 16y) = 9 − 24
5x = -15
Solve for x.
x = -3
Now you can plug this into either equation to find y.
-3(-3) + 16y = 9
9 + 16y = 9
y = 0
The solution is (-3, 0).