Question 1022954
The normal set up for work problems is
{{{t/A + t/B = 1}}}
In our problem, A completes 7/10 of the job in 14 days.  That means he could do it all in 20 days.
Our t in the set up is 2 days, and the 1 job in the set up is only 3/10 job here.
So our equation looks like this
{{{2/20 + 2/B = 3/10}}}
and when you work that out you find
B = 10 days