Math help

a + b = 9   →  b = 9  -a

a*b = 20   →  a(9 - a) = 20  → -a² + 9a = 20 →   a² - 9a + 20 = 0   and factoring, we have (a - 5) (a - 4) = 0

So  a  = 4 or 5    ....either way, we will be adding the fractions

1/4 + 1/5   =  9 / 20  = .45

$$a*b =\frac{1}{a} + \frac{1}{b} Hence: a*b = (a+b)/(a x b) a+b = 9 , a x b = 20 a*b = 0.45$$