Given,

ABCD is an isosceles trapezium.

AB || CD

AB = 20 cm

CD = 10 cm

Length of each leg of trapezium = 13 cm

By the formula, the area of trapezium is:

Area of trapezium = (a+b)h/2

where a and b are parallel sides and h is the height of the trapezium.

Height of triangle, h2 = 132 – 52

h2 = 144

h = 12cm

Area of trapezium = 1/2 ×(sum of parallel sides) × (height)

= 1/2 × (10 + 20) × 12

= 180 sq.cm