if the point(x,3√3)is on the unit circle, what is x?

The unit circle has a radius of one and is centered at the origin; therefore, every value for x must be in the range  -1 ≤ x ≤ 1  and every value for y must also be in the range  -1 ≤ y ≤ 1.

3√3 is outside the unit circle.