Let the capaciteis of one man and one boy be m and b respectively
Given
`4m+6b=(1)/(2)`
That is, `2m+3b=(1)/(6)`
Also, `m+3b=(1)/(36)`
Eqs.(1)-(2) gives, `m=(1)/(4)-(1)/(6)=(1)/(36)`
`m+b=(1)/(12)+(1)/(36)=(1)/(9)`
`:.` 1 mand and 1 boy can complete the work in 9 days