Hi.
The ramp is a triangle! So the first thing we might want to do is draw a triangle. I can't do that in this space, but you can!
You'll want to make the bottom of the triangle (the base) 24 meters long. So use a scale - one centimeter in your drawing equals one meter in "real life." The base would be drawn 24 cm long on your drawing.
The ramp's height is the straight line that runs upward from the base. It's 7 meters. So make that 7 cm long in your drawing.
Since you're dealing with a triangle, you can use the Pythagorean Theorem to figure out the length of the diagonal side ("hypotenuse").
Here's how it works:
a2 + b2 = c2
where a and b are the length of the two sides (base, height) and c is the length of the hypotenuse.
We know a and b from the problem - 24 meters and 7 meters. So let's plug them in:
242 + 72 = c2
576 + 49 = c2
625 = c2 (take the square root of 625)
c = 25 m
And there it is!!