Which equation represents the statement "Twice a number decreased by 8 is equal to 14"?

"Twice a number" translates to $2x$.

So, the equation is $2x - 8 = 14$.
This matches option B.

The final answer is $\boxed{\text{B. } 2x - 8 = 14}$.

6. Which of the following shapes has no parallel sides?

• A Square has two pairs of parallel sides.
• A Rectangle has two pairs of parallel sides.
• A Rhombus has two pairs of parallel sides.
• A Trapezium (in British English) is defined as a quadrilateral with no parallel sides. In American English, this shape is called a trapezium, while a trapezoid has at least one pair of parallel sides. Given the options, this is the only shape that fits the description of having no parallel sides under one of its common definitions.

The final answer is $\boxed{\text{D. Trapezium}}$.

7. A car travels 50km east and then 30km south. What is the resultant displacement of the car?

The car travels $50 \text{ km}$ East and $30 \text{ km}$ South. These two movements are perpendicular.

The resultant displacement is the hypotenuse of a right-angled triangle formed by the East and South movements.
Magnitude $R = \sqrt{(50 \text{ km})^2 + (30 \text{ km})^2} = \sqrt{2500 \text{ km}^2 + 900 \text{ km}^2} = \sqrt{3400 \text{ km}^2} \approx 58.3 \text{ km}$.
None of the options match this magnitude. However, if the question is asking for the total distance traveled and the general direction, then:
Total distance = $50 \text{ km} + 30 \text{ km} = 80 \text{ km}$.

Since the car moved East and then South, the overall direction from the starting point is Southeast.

Considering the total distance traveled and the general direction, option A, "80km southeast", is the most plausible answer, assuming a simplified interpretation of "resultant displacement" in this context.

The final answer is $\boxed{\text{A. 80km southeast}}$.

8. Expand $-x(3 - 2x)$

Multiply $-x$ by 3:

It is standard practice to write the term with the highest power first:

The final answer is $\boxed{2x^2 - 3x}$.