Answer:
x = 11, arc RB = 150°
Explanation:
The secant- secant angle RDB is calculated as half the difference of its intercepted arcs, that is
∠ RDB =
( RB - EC ), that is
5x - 10 =
( 13x + 7 - 60 )
Multiply both sides by 2 to clear the fraction
10x - 20 = 13x - 53 ( subtract 13x from both sides )
- 3x - 20 = - 53 ( add 20 to both sides )
- 3x = - 33 ( divide both sides by - 3 )
x = 11
Thus
arc RB = 13x + 7 = 13(11) + 7 = 143 + 7 = 150°