Question

Please help with #12

Answer 1

ACD = 76

Explanation:

The sum of the interior angles of a triangle total 180 degrees.

The sum of the two angles making up a straight line also total 180 degrees.

In the triangle, we have A + B + C = 180.

On the straight line, we have C +
`C^(1)` = 180, so C = 180 -
`C^(1)`

We now have A + B + (180 -
`C^(1)`) = 180

A + B -
`C^(1)` = 0

(4x + 15) + 21 - (7x + 6) = 0

3x = 30

x= 10

Therefore ACD = 7x + 6 = 76