Question

x varies partly as y and partly y^2 when y =4,x=52.8 ,and when y=5,x=81 find x when y=6

Answer 1

Your use of "partly" is not understood. If your teachers uses this term, I suggest drop the class, you are headed for more made up math that is not understood by many math users.

Answer 2

However, in the interests of passing this class, "varies partly" means
x = ay + by^2
Now plug in your points to find a and b:
4a + 16b = 52.8
5a + 25b = 81
Then use your function to find x(6)

Answer 3

Good job

Answer 4

More explanation