Write an equivalent expression by distributing the "−" sign outside the parentheses: -(-9.1d-6f+9.1)

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

Having a hard time understanding this question (see attachment).

Atruck can be rented from company a $50 a day plus $0.60 per mile. company b charges $20 a day plus $0.80 per mile to rent the same truck. find the number of miles in a day at which the rental costs for company a and company b are the same