I need some help 7th grade math

Autility company burns coal to generate electricity. the cost c(p), (in dollars) of removing p percent of the some stack pollutants is given by c(p)= 85000p/100-p a) find the cost to remove 30% of the pollutant b) find where the function is undefined

Beth took out a $20,000 loan for college she is borrowing money from two banks. bank a charges an interest rate of 8.5% bank b charges and interest rate of 10.5% after one year alice owes $1860 in interest how much money did she borrow from bank a

Hiroaki wants to find 3 3/4 - 7/8 explain why he must rename 3 3/4 to do the subtraction.