Answer:
∠B = 65°; ∠C = 115°
Step-by-step explanation:
The first thing you to do is set <u>∠B and ∠D equal to each other. </u>
The reason you do this is because the oppisite angles are equal to each other in a parallelogram.
Next, you want to start simplifying the equation (I personally like to start with the variables).
Then, you simplify again (you can combined these if you want but for example I am breaking it down more.
Then you dived by 3, and you get 15=n. Now (and people often forget this step) you have to plug it back in to solve for the equartion. ∠B=3(15)+20, <em><u>∠B=65</u></em>. Now you have to subtract 65 from 180 because <u>∠B and ∠C are completmtry</u>. 180-65=<u><em>115=∠C</em></u>