Zero on the x-axis is the origin, (0,0) so the distance from the origin to (4,7) is going to be, according the the Pythagorean Theorem...
d^2=x^2+y^2
d^2=4^2+7^2
d^2=16+49
d^2=65
d=√65 since √65=√(5*13) and 5 and 13 are both prime this cannot be simplified any further...
So the distance is just √65 units. (approximately ≈8.06 units)