Can someone please simplify this? :)
9x(8 * 9y) + 4

Simplify a7/a4 a) 1/a3 b)-a/a2 c)a4/a3 d)a3

Trish receives $450 on the first of each month. josh receives $450 on the last day of each month. both trish and josh will receive payments for next four years. at a discount rate of 9.5 percent, what is the difference in the present value of these two sets of payments?

Anyone know? will mark brainliest if you're correct!