Answer:
21.25
Explanation:
We can use the Pythagorean theorem to solve
We have the two legs and are looking for the hypotenuse
a^2 + b^2 = c^2
17^2 +12.75 ^2 = c^2 where c is the diagonal
289 +162.5625 = c^2
451.5625 = c^2
Take the square root
sqrt(451.5625) = sqrt(c^2)
21.25 =c