Someone, please help me

The variable z is directly proportional to x, and inversely proportional to y. when x is 4 and y is 13, z has the value 1.2307692307692. what is the value of z when x= 9, and y= 20

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.

Multiply. write your answer in simplest form. 3/8 x 5/7