What is 4 1/2 - 3 5/12 in a mixed number in lowest terms? ?

Add the whole numbers first: 4 - 3 is 1
Then find a common denominator, in this case use 12 because 2 divides into evenly.
Multiple 1/2 by 6/6 (which is like multiplying by 1) to get 6/12.
Then subtract the numerators of the fractional remainders only 6-5 is 1.
DO NOT subtract the denominators.  In addition and subtraction a fraction's denominator remains unchanged.
Combine results 1  and 1/12.