The best way to solve one of these types of problems in my experience is to make those whole numbers into fractions so that way the subtraction will be easier.
For 4 and 3/8 we have a total of 35/8. (Keep in mind 4 can be represented as 32/8. then we add the 3/8.)
For 1 and 5/8 we have a total of 13/8. (Keep in mind the 1 can be represented as 8/8 and we add the 5/8)
Now if we do the subtraction 35-13 we end up with 22/8 which can be simplified to 11/4 or if you prefer to use decimals 2.75.
Best of Luck!