Answer:
40
Explanation:
Remark
The catch is that all of the sides given are radii of a circle (the circumcircle in this case.)
Take and two given lines. Equate them. Solve for x. Then go back and substitute x for RC.
Equation
PC = RC
3x + 7 = 5x - 15
Solution
3x + 7 = 5x - 15 Add 15 to both sides
3x + 7 + 15 = 5x - 15 + 15 Combine like terms
3x + 22 = 5x Subtract 3x from both sides
3x - 3x + 22 = 5x - 3x Combine like terms.
22 = 2x Switch and divide by 2
2x/2 = 22/2 Solve
x = 11
Answer
RC = 5x - 15
RC = 5*11 - 15
RC = 55 - 15
RC = 40