Explanation:
there are a few things from school everybody has to burn into their brains for life. one of them : Pythagoras for right-angled triangles :
c² = a² + b²
c is the Hypotenuse (the triangle side opposite of the 90° angle), a and b are the triangle legs.
now, it depends on what you teacher agreed with you regarding naming the sides of such a triangle.
sometimes "base" is the Hypotenuse (baseline), sometimes it is one of the legs, and then the height is the second leg (as the legs are standing at a 90° or right angle at each other).
we have to assume the second one, as for the first one we have not enough information to solve the question (because with just a given Hypotenuse and the height to the Hypotenuse we can draw infinitely many different triangles with different perimeters).
so, we have
Hypotenuse² = 24² + 7² = 576 + 49 = 625
Hypotenuse = sqrt(625) = 25 m
the perimeter of the triangle is then
25 + 24 + 7 = 56 m