Hi,
First you need to find the least common denominator. So in this case it's 8. So now we must convert the rest of the fractions. 1 1/2 would become 1 4/8, 3/4 would be 6/8 and 1/8 would remain the same. If you add them together you get 2 3/8 cups. To put them on a number line you would label it like so:
----1---I---I---I---I---I---I---I---2---I---I---I---I---I
^ 1 1/8 ^1 7/8 ^ 2 3/8
Sorry for the horrible representation haha.
Have a great day!