Answer:
x = 15 
Step-by-step explanation:
As we can see it is an isosceles triangle so 
The perpendicular line joining the vertex and base of isosceles triangle bisects the base. so 
Taking the triangle of right side 
hypotenuse (h) = 25 inches 
base (b) = 20 inches 
perpendicular (p) = x = ? 
We know by using Pythagoras theorem 
p= √h² - b² 
x = √ 25² - 20²
 = √ 225
x =15
Hope it will help :)