r * t = w
Say w = 1
Sal can complete the job in 5 hours.
r * 5 = 1
r = 1/5

When Sal and Pathik work together, they can finish the job in 3 hours.
Since they work together, Sal and Pathik's rates added * 3 (total time) = 1 (total work)
From here, you can create an equation:
P = pathik's rate
(1/5 + P)* 3 =1
3/5 + 3P = 1
3P = 2/5
P = 2/15

Pathik's rate = 2/15
2/15 * 3 (total work time when working together ) = ?
? = 6/15 meaning Pathik in 3 hours has done 6/15 of the work
6/15 = 2/5*100 = 40
Pathik has done 40% of the work in the three hours, meaning the answer is C.