Using the law of sines to solve the triangle if..
Parallel line means the same slope
（8-1）/(-17-a)=(1-5)/(a+2)
so a is 18
This is a simple multiplication, written in a strange form.
5(t+2) means 5 x t + 5 x 2 which simplifies to:
5t + 10
If it's equal to a number, 0 for example, then with a little rearranging we can find what t is.
5t + 10 = 0,
5t = -10
t = -2
If it's not equal to something, the answer is just 5t + 10.
