C. 110. This is because all triangles add up to equal 180*. So you add the two angles you have and subtract from 180.
351 because 293 multiplied by 3 = 879, and 1230 - 879 = 351
You want to end up with
. Expand this using the angle sum identity for sine:

We want this to line up with
. Right away, we know
.
We also need to have

Recall that
for all
; this means

Then

So we end up with

-3z + 7 = -7 - 10z
Add 10z to both sides
7z + 7 = -7
Subtract 7 from both sides
7z = -14
Divide by 7
Z = -2
Slope of perpendicular is -1/3.
Then equation is
y-5=(-1/3)(x+9)