B and C for the first two
Those are adjacent angles. They equal 180 degrees.
10x-20+6x+8= 180
16x-12=180
Add 12.
16x= 192
x=12
I hope this helps!
~kaikers
To find the average rate of change in a interval

We use the following formula:

Applying this to our interval

We have the following rate of change:

We have an average rate of change equals to 6.