
Lauren H. answered 10/27/18
Experienced High School Chemistry Teacher
x + y = 15, y = 15 - x
1/x + 1/y = 5/18
1/x + 1/(15 - x) = 5/18
(15 - x) + x = (5/18)(x)(15 - x)
15 = (5/18)(15x - x^2)
15 = (75/18)x - (75/18)x^2
- (75/18)x^2 + (75/18)x - 15 = 0
-75x^2 + 75x - 270 = 0
-25x^2 + 25x - 54 = 0
x = .5 - 1.4
x = .5 + 1.4