Question

Algebra 2.. Please help!

Answer 1

Only C works because -168 +160 gives -8

Answer 2

Given 
$\left \{ {{2x-4y=24} \atop {-6x+20y=-8}} \right.$,
we can use Gaussian elimination to find the point of intersection.

Let's find a term we want to cancel. We could either multiply the first equation by 3 to cancel the x-terms, or multiply by 5 to cancel the y-terms.

$5(2x-4y=24) = 10x-20y=120$


$10x-20y=120 \\ \\ -6x+20y=-8 \\ \\ \\ 4x=112 \\ \\ x = 28$

We have now solved for x, but we need to find y. We can substitute our value for x back into any of the two equations.

$2(28)-4y=24 \\ \\ 56-4y=24 \\ \\ -4y=-32 \\ \\ y = 8$

So, the point is (28, 8).

Answer choice C.

If your teacher doesn't require you to show your work (and this tip is especially useful for the SAT and ACT), you can save a lot of time by simply plugging-in the solutions from the answer choices to see which one works.