First, take all the sides you already have, then add them up. (You should get 12) To find the other two sides, do some more simple addition. The 2+3+2 of the the top side add up to six (the bottom side) and sides equal each other so add another three. Total is 12+6+3=21
Answer: 
Step-by-step explanation:
If we draw RP and PS, then in the quadrilateral formed, we know that
, and since angles in a quadrilateral add to 360 degrees, this means
.
Thus, arc RS also measures 126 degrees
Rational because the answer was simplified already as 12÷4=3