So the diameter of 0,76 is 1,52 and the circumference is 4,78 and area is 1,81(corrected to two decimal places)

But now what is the diameter,circumference and area of x

Hmmm. so, given the radius, you have come up with the corresponding diameter, circumference and area.

I have no idea what x is supposed to be, but if it is an unknown radius, then recall that

area = pi x^2

and you can review the formulas for the other quantities.