Help, idk what this answer is

How do you use the additive inverse to evaluate an expression that uses subtraction in a full sentence

Find the least common denominator for thesetvo rational expressions. n^2/n^2+4n+4 -3/n^2+7n+10

Heather is a cashier. she can ring up 1212 customers in 99 minutes. at this rate, how many minutes does it take her to ring up 44 customers?