Kelly has save $35 to take music classes. She must pay a registration fee of $15 and then an additional $5 for each class. Which equation will Best help kelly determine the number of classes she can afford

Mr. len is a teacher whose salary is $22,570 for this school year, which is 185 days. in mr.lens school district, substitute teachers are paid $80 per day. if mr. len takes a day off without pay and a substitute teacher is paid to teach his classes how much less does the school district pay in salary by paying a substitute teacher instead of paying mr.len for that day?