Pretend there are lines drawn between the points making a right angle triangle. Now use Pythagorean Theorem to solve (x^2 + y^2 = hypotenuse^2)
In this case
2^2 + 7^2 = hypotenuse^2
4+49=hypotenuse^2
53=hypotenuse^2
square root of 53=hypotenuse
7.28=hypotenuse
ROUNDING:
7.3 units between the two points