For the first one, 1 1/2 + 1 1/2 = 3
To find this out, take what we know, the 1 1/2 and subtract that from the final answer, 3.
That leaves us with the missing number.
Same with the rest of them, subtract the number that is know from the total.
#3 is 2 1/2
#4 is 1/4
#5 is 1 1/4
Hope this helps!