A trapezoid's parallel sides are 8 decimeters and 18dm, the other sides are 8.1dm and 5dm.
How do I find surface area and height of the trapezoid? We're studying trigonometry at the moment, but I can't think of any way to solve it this way, so I need your help, thanks.

Anyone please?

When only the side lengths are known, you can use this formula:

A=\frac{a+c}{4(a-c)}\sqrt{(a+b-c+d)(a-b-c+d)(a+b-c-d)(-a+b+c+d)}

where a \|| c and: a > c

Then using:

A=\frac{(a+c)h}{2}

and therefore:

h=\frac{2A}{a+c}

you can calculate the height.

Okie, thanks a lot :).