A - 90 degrees
B - 110 degrees
C - 78.5 =
5 to the second power
D - 15.3
To find A, the point of intersection of a tangent to the center of a circle always makes a 90 degree angle.
To find B, do 360 subtracted by all known angles while keeping in mind the angle opposite to RST.
To find C, use the formula to find an area of a circle. In this case, OP = pi r squared.
To find D, you need to realize that it is just a fraction of the circle which is 70 degrees. So you need to use the fraction to find the answer, to do so you use (70/360) times 78.5 which gets you 15.3.
Hope this helps!