Let's break down the problem in the image step-by-step. The question is in Malay, and it translates to:

"The perimeter of a rectangle is exactly 70 cm. The width of the rectangle is $\frac{2}{5}$ of its length. What is the width of the rectangle?"

Let's solve this problem:

1. Perimeter of a Rectangle Formula:
   The perimeter $P$ of a rectangle is given by the formula: $P = 2 \times (\text{length} + \text{width})$ Here, $P = 70$ cm.

2. Width in Terms of Length:
   Let the length be $L$.
   According to the problem, the width $W$ is $\frac{2}{5}$ of the length: $W = \frac{2}{5}L$

3. Substitute into the Perimeter Formula:
   Substitute $W$ into the perimeter formula: $70 = 2 \times \left(L + \frac{2}{5}L\right)$

4. Simplify the Equation: $70 = 2 \times \left(\frac{5}{5}L + \frac{2}{5}L\right)$ $70 = 2 \times \left(\frac{7}{5}L\right)$ $70 = \frac{14}{5}L$

5. Solve for $L$: $L = \frac{70 \times 5}{14}$ $L = \frac{350}{14}$ $L = 25$

6. Find the Width: Now that we have the length $L = 25$: $W = \frac{2}{5} \times 25$ $W = 10$

The width of the rectangle is 10 cm. Therefore, the answer is B. 10.

Would you like more details or have any questions?

Here are 5 related questions to expand on this topic:

1. What is the formula for the area of a rectangle?
2. How would you find the length if you only knew the perimeter and the width?
3. How can the perimeter formula be rearranged to solve for width directly?
4. What is the difference between perimeter and area?
5. Can the properties of a rectangle be applied to other quadrilaterals?

Tip: When solving word problems, always translate the given information into mathematical expressions before attempting to solve them.