Mr. Thaxton has two daughters. The sum of their ages is twenty-one. The product of their ages is one hundred ten. How old is Mr. Thaxton's youngest daughter?

A.

9

B.

10

C.

11

D.

12

B. 10

Step-by-step explanation:

x + y = 21

xy = 110

Rewrite first equation. x + y = 21 becomes y = - x + 21

Now substitute this new equation in the second equation.

x (-x+21) = 110

-x^2 + 21x - 110

Divide by - 1

x^2 - 21x + 110

(x - 10) (x - 11)

x = 10, 11

10 is less, so the youngest daughter is 10