Answer:
5 is the height
Explanation:
With parallelogram it usually shows the lengths and we find the height using either diagonal or triangle within the shape or in some extremes use the exterior.
The height must be perpendicular to either set parallel lines for it to be an equal equation of H x Adjacent Length = Area
Where we find L x W of a normal rectangle of 90 degree angles = Area of a rectangle, we find that parallelograms have diagonal sets of acute angles under 90 degree, and diagonal sets of obtuse angles (over 90 degree) where all angles just like rectangles/squares add up to 360 degrees.
We can see in the exterior of the triangle a trapezoid surface area and therefore reflects the same length as the missing measure being the length to make the area = 15units.
Here we can prove, height of 5 = length 5 = hypotenuse of 5 (of a right sided triangle).