
Let the length of DP be \( x \). Since \( DP = AB \), it follows that:
\[ AB = x \]
Given that \( DP = CP \), the total length \( CD \) is:
\[ CD = DP + CP = x + x = 2x \]
Let the height of the trapezium be \( h \).
The area of a parallelogram is calculated as base × height:
\[ \text{Area}_{ABPD} = AB \times h = xh \]
Triangle BPC is a right triangle with base \( x \) and height \( h \). Its area is:
\[ \text{Area}_{\triangle BPC} = \frac{1}{2} \times x \times h = \frac{1}{2}xh \]
The problem states that the area of the parallelogram minus the area of the triangle equals 10:
\[ xh - \frac{1}{2}xh = 10 \Rightarrow \frac{1}{2}xh = 10 \Rightarrow xh = 20 \]
The trapezium has parallel sides \( AB = x \) and \( CD = 2x \), with a height \( h \). The area is calculated as:
\[ \text{Area}_{ABCD} = \frac{1}{2}(AB + CD) \times h = \frac{1}{2}(x + 2x)h = \frac{1}{2}(3x)h = \frac{3}{2}xh \]
Using the previously determined value \( xh = 20 \):
\[ \text{Area}_{ABCD} = \frac{3}{2} \times 20 = 30 \]
Option (D): \( \boxed{30} \)