
Actually Welcome to the Concept of the trigonometry.
Here, since the triangle is right angles, with perpendicular = x and hypotenuse = 14 , and one angle = 25°
to get the value of x, we use the sine ratio.
hence, Sin(25°) = x/14
hence, x = sin(25°)*14 ==> 5.90
hence the value of x = 5.90 units.