Question

Find measure of <_B.

Answer 1

Firstly, we need to find m<BCA

<BCA+<BCD=180°

m<BCD=111°

<BCA+111°=180°

m<BCA=69°

Secondly, we need to find y

The sum of all angles of triangle is equal to 180°, so

`4y + 3y + 6 + 69 = 180 \\ 7y = 105 \\ y = 15`

Now we can find m<B

m<B=(3y+6)°

y=15

m<B=3×15+6=51°

Answer: m<B=51°