Question

Descubra o X

1/20 = 1/30 + 1/x

Answer 1

1/20 - 1/30 = 1/x 
(30-20)/600 = 1/x
10/600 = 1/x
1/60 = 1/x
x=60 

Answer 2

$\frac{1}{20}=\frac{1}{30}+\frac{1}{x}\\ \\ mmc(20,30,x)=60x\\ \\ \frac{3x}{60x}=\frac{2x+60}{60x}\\ \\ 3x=2x+60\\ \\ 3x-2x=60\\ \\ \boxed{x=60}$