Use Pythagorean Theorem:
[tex] a^{2} + b^{2} = c^{2} [/tex]
[tex] 7^{2} + 24^{2} = c^{2} [/tex]
[tex] 7^{2} + 24^{2} = c^{2} [/tex]
[tex] 49 + 576 = c^{2} [/tex]
[tex] 625 = c^{2} [/tex]
[tex] 25 = c [/tex]
(You could also memorize that 7-24-25 is one of the "integer triples" that satisfies the Pythagorean Theorem. Other common ones are 3-4-5 and 5-12-13.)
