1 boy and 2 girls can do a work in 10 days. 2 boys and 1 girl can do a work in 8 days. How long will 1 boy and 1 girl take to do the work?

1boy + 2 girls = 1/10 th part in one day
2 boys +1 girl =1/8 th part in one day

So,10b+20g work =16boys +8girl work
Equating them 6 boys=12 girls i.e 1boy = 2girls

1b+2girls in 10days --> 4girls in 10days
Asked 1b+1girl--> 3girls can do it in x days
Solving it they will do it in 7.5 days.