Answer:
He will finish the rest of the problems in 32.4 minutes.
Explanation:
Since we are given that Yan has completed 3/5 of 45 problems i.e.


Thus he has completed 27 problems
Remaining no. of problems are 45-27 = 18
Since he complete each problem in minutes =

So, he completes 18 problems in minutes = 18 *1.8 = 32.4 minutes
Hence , He will finish the rest of the problems in 32.4 minutes.