Question 954671
The restriction of No Trigonometry doesn't seem right.  I drew a neighboring isosceles triangle to form a parallelogram to help understand the values given and findable.  Tough to show here, but free-hand I could draw the picture.  Used cosine and sine, and half of length equivalent to half the base.


Altitude forms two angles at top of given triangle 15 degree each.


AREA?
{{{(1/2)(2*20*sine(15))*(20*cos(15))}}}