These are hard problems

Ataxi cab charges $1.75 for the flat fee and $0.25 for each time. write an in equality to determine how many miles eddie can travel if he has $15 to spend.

Diane’s bank is offering 5% interest, compounded monthly. if diane invests $10,500 and wants $20,000 when she withdrawals, how long should she keep her money in for? round to the nearest tenth of a year.

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.