Respuesta :

right triangle has one degree = 45 so it's isosceles right triangle.
let y = hypotenuse of small isosceles right triangle 

y^2 = 7^2 + 7^2
y^2 = 49 + 49
y^2 = 98

so 
x^2 = 98 + 98
x^2 = 196
x = 98

answer
x = 98