I need help on these please help me smart people

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

Marya wants to factor the polynomial 36x^3 -22x^2 - 144x.which term can she add to the polynomial that would not change its grestest common factor? check all that apply

When x = 3 and y = 5, by how much does the value of 3x2 – 2y exceed the value of 2x2 – 3y ?