Given that the trapezium is isosceles. Therefore from the fig. it is clear that SM = NR = 3cm

Also, PQ = MN = 7cm

Now, length of side SR = 3 + 7 + 3 = 13cm

Therefore, the sum of parallel sides of trapezium = 7 + 13 = 20

And the distance between them = 4 cm

= 40 sq cm