Question

which of the following angles can you add together to epual angle d?

Answer 1

Note that angles c and d are supplementary. Hence, you have

$c+d\text{ = 180}$

Note that a, b and c are the inner angles of a triangle. We will use the following fact: The sum of the inner angles of a triangle is 180°. Then

$a+b+c=180$

If make this equations equal, we get

$c+d=a+b+c$

If we cancel c out from both sides, we get

$d=a+b$

so we should add angles a and b to get the value of angle d