Correct Answer - Option 3 : 6 cm

**Given:**

parallel sides = x + 3 and 2x + 7

height 18 cm

The area of trapezium = 144 sq. cm

**Concept used:**

The area of trapezium = (1/2) × h × (sum of parallel sides)

**Calculation:**

sum of parallel sides = x + 3 + 2x + 7 = 3x + 10

144 = (18/2) × (3x + 10)

3x + 10 = 144/9 = 16

Then, x = 2

Difference between parallel sides = 2x + 7 - (x + 3) = (4 + 7) - (2 + 3)

**∴ The difference between parallel sides is 6 cm.**