Question

I don't quite understand the process needed here, so if anyone can help explain I would really appreciate it!

Answer 1

Explanation:

The angle at F is

180 - 17x + 7 = straight line = 173-17x

Now the sum of the interior angles of the triangle = 180

173 - 17x + 13x+3 + 40 = 180

-4x = -36

x = 9

Answer 2

Check the picture below.

`17x+7=40+(13x+3)\implies 17x+7=13x+43\implies 17x=13x+36 \\\\\\ 4x=36\implies x=\cfrac{36}{4}\implies \boxed{x=9}`