Answer:
sqrt(172) = hypotenuse
Explanation:
IF those are the leg lengths (sides) and not the hypotenuse, then use Pythagorean theorem
c^2 = 7^2 + sqrt (123) ^2
c = sqrt (172)
If sqrt 172 is the hypotenuse :
(sqrt123)^2 = 7^2 + x^2
then x = sqrt (74 )