60/(20+x)+60/(20-x)=6,25
(60/(20+x)+60/(20-x))*(x+20)=6,25*(x+20)
-2400/(x-20)=6,25x+125
(-2400/(x-20))*(20-x)=(6,25x+125)*(20-x)
2400=2500-6,25x²
6,25x²-100=0
6,25x²=100
x²=100/6,25
x²=16
x=²√16
x=4
60/(20+x)+60/(20-x)=6,25
(60/(20+x)+60/(20-x))*(x+20)=6,25*(x+20)
-2400/(x-20)=6,25x+125
(-2400/(x-20))*(20-x)=(6,25x+125)*(20-x)
2400=2500-6,25x²
6,25x²-100=0
6,25x²=100
x²=100/6,25
x²=16
x=²√16
x=4