We should find a number that satisfies the Pythagorean triple.
a and b are the legs and c the hypothenuse.
a²+b² = c²
we should find a or b.
So, form the squared hypothenuse subtract the squared known leg.
a² (or b²) = c²-a² (or b²) = 25²-7² = 625-49 = 576 (this is the unknown leg squared).
To find the measure of the leg, square root 576.
a (or b) = √576 = 24 cm