Altitude of a trapezoid? How?

[HomeWork14]

Altitude of Trapezoid?
I need help with this, I have been working on it for a few days but I still seem to be doing something wrong,
I know that its the perpendicular distance between the two parallel sides.

Can Someone please show me how to work out this problem or the formula for altitude of a trapezoid?

Trapezoid has equal nonparallel sides, the upper base is 6, the lower base is 16, and the diagonal is 12, what is the altitude of the trapezoid?
:?:
How do I calculate the altitude of a trapezoid?
:?:

Thank You

 

[morson]

Is this what you mean?

The two little triangles at the end are congruent (by the side-side-side proof).

By Pythagoras' theorem, 11^2 + h^2 = 12^2

... could be wrong though.