Answer:
x = 17, MN = 11
Explanation:
Given 2 secants from an external point to a circle, then
The product of the external part and the whole of one secant is equal to the product of the external part and the whole of the other secant.
(5)
7(7 + x) = 8(8 + 13) = 8 × 21 = 168 ( divide both sides by 7 )
7 + x = 24 ( subtract 7 from both sides )
x = 17
(6)
9(9 + 2x - 7) = 10(10 + 8)
9(2x + 2) = 10 × 18 = 180 ( divide both sides by 9 )
2x + 2 = 20 ( subtract 2 from both sides )
2x = 18 ( divide both sides by 2 )
x = 9
Then
MN = 2x - 7 = 2(9) - 7 = 18 - 7 = 11