X=time of the third person it would take to fill the pool
We can suggest this equation:
6[(1/20) + (1/15) +(1/x)]=1
6[(3x+4x+60)/60x]=1
(7x+60)/10x=1
7x+60=10x
7x-10x=-60
-3x=-60
x=-60/-3
x=20
Answer: the third person alone would fill the pool in 20 hours .
Probably it's all wrong
4.5 = 10 %If is the same then 4.5*20+45=135
If not then
FV=P(1+r)n45* (1+0.1)20 = 45*6.727=302.737
Yuto is correct because he isolated the variable correctly and reversed the inequality symbol.
x < 3
