`x/(2*2)+x/(3*4)+x/(6*4)+x/(8*5)+x/(10*6)=5`
`x/4 +x/12 +x/24 +x/45 + x/60 =5`
`x(1/4 +1/12 +1/24 +1/40 +1/60)=5`
`x( (30+10+5+3+2)/120 ) =5`
`x *50/120 =5`
`x = 5 *120/50 =12`
\(\dfrac{x}{4}+\dfrac{x}{12}+\dfrac{x}{24}+\dfrac{x}{40}+\dfrac{x}{60}=5\)
\(\Leftrightarrow x\left(\dfrac{1}{4}+\dfrac{1}{12}+\dfrac{1}{24}+\dfrac{1}{40}+\dfrac{1}{60}\right)=5\)
\(\Leftrightarrow x.\dfrac{5}{12}=5\)
\(\Leftrightarrow x=12\)