Can someone me solve and explain?

question:

suppose a different tournament that eddie organizes has 120 players and the entry fee is $40. each time he increases the fee by $5, he loses10 players. determine what the entry fee should be to maximize the value of the pool.

The school that imani goes to is selling tickets to the annual dance competition. on the first day of the ticket sales the school sold 7 adult tickets and 5 child tickets for a total of $96. the school took in $40 on the second day by seling 3 adult tickets . find the price of an adult ticket and the price of a child ticket. solve by using substitution elimination college prep algebra math heres the 2 equations i came up with 7x+5y=96 and 3x+2y= -40 show all workiv be stuck on this.

Find the quotient 9(cos135+isin135)/7(cos10+isin10)

In a rational number twice the numerator is 2 more than the denominator. if 3 is added to each, numerator and the denominator, the new fraction is 2/3. find the original number