What is 6 1/2 - 1 9/10

Find common denominator which is 10 then find the equivalent fraction for 6 1/2  = 6 5/10.
Now you have 6 5/10 - 1 9/10, but since first numerator is less than the second numerator you need to borrow from the whole number. 6 5/10 = 5 10/10 + 5/10 = 5 15/10. Now just subtract the whole numbers and the numerators.
5 15/10 - 1 9/10 = 4 6/10 simplify to 4 3/5.