Question

Jenny spent 35 minutes doing research on the internet. She finished at 7:10 p.m. At what time did Jenny start her research?

Answer 1

she started at 6:35 p.m, 
because minus 10 from the 7:10, you just have 7 now right? And she only has 25 min left. then minus 25 from 60 to get your answer. it is 6 35 pm.

Answer 2

We'll go to the nearest hour, which is 7:00 pm
7:00 pm is 10minutes before the time she finished so we can subtract 10 minutes from the total time 35minutes-10minutes=25minutes

in an hour there is 60 minutes
so 60-25=35 minutes
And because we are subtracting to find the time she started we know she couldn't have started at or before 7:00pm

so...she started her research at 6:35pm