It took 2/3 of an hour to complete her science homework. it took bethany 3/4 of the amount of time to do her math homework as her science homework. how many more minutes did it take bethany to complete her science than her math homework

We know there are 60 minutes in an hour.  To find 2/3 of an hour we divide 60/3 to find 1/3 and multiply by 2 so:
60/3 = 20
20*2 = 40 minutes (which is 2/3 of an hour) to do science

We do the same thing with the 40 minutes.  To find 1/4 of 40 minutes we divide 40 by 4 and then multiply it by 3 to get 3/4 so:

40/4 = 10
10*3 = 30 minutes

Then subtract the times 40-30 = 10 minutes

It took her 10 more minutes to complete her science homework.

Hope that helps