Question

The triangles are similar.

Answer 1

7,24,25 ~ x,72,75

so x/7 = 72/24 = 75/25 = 3
then x = 7*3 = 21

Answer 2

Picture of the triangles is missing so let's draw two similar triangles ABC and DEF. Both are right angle triangle because hypotenuse occurs only in right angle triangle.

AB=72, AC=75, BC=x

DE=24, DF=25, EF=7

Now we can solve this problem in two ways.

Either use ratio for similar triangles or use Pythogorean theorem.

Taking ratio will be easy so let's do that.

Given that both triangles are similar so ratio of corresponding sides will be constant.

$\frac{BC}{AB}=\frac{EF}{DE}$

$\frac{x}{72}=\frac{7}{24}$

$\frac{x}{72}*72=\frac{7}{24}*72$

$x=\frac{504}{24}$

x=21

Hence final answer is x=21.