How much is 3/4 of 120? and how much is 3/8 of 160?

3/4 of 120
=3/4*120
=360/4
=90

3/8 of 160
=3/8*160
=480/8
=60

3/4 of 120 would be 90.
If you divide 120 into 4 equal parts, each part would be worth 30, because 30 multiplied by 4 is 120. So, to find how many 3 parts would equal, you add 30 plus 30 plus 30. 
You get 90. So, Megan has 90
3/8 of 160 would be 60 
If you divide 160 into 8 equal parts, you get 20 for each part, because 20 multiplied by 8 is 160. So to find how many 3 parts would equal, you add 20 plus 20 plus 20.
you get 60. So, Alex has 60.
The question is asking you how many more Megan has. Well, Megan has 90, and Alex has 60. 90 - 60 is 30.
Your answer would be 30.
I hope this helped