To solve this problem, we need to calculate the surface area of the given solid. The figure appears to be a triangular prism, where the triangular faces are on the top and bottom, and the three rectangular faces connect the corresponding sides of the triangles.

Step 1: Identify the components

• Base of the triangle: 13 cm
• Height of the triangle: 21 cm
• Length of the prism (distance between the two triangular faces): 35 cm

Step 2: Area of the triangular faces

The area of a triangle is given by:

$\text{Area of triangle} = \frac{1}{2} \times \text{Base} \times \text{Height}$

Substituting the values:

$\text{Area of each triangular face} = \frac{1}{2} \times 13 \, \text{cm} \times 21 \, \text{cm} = 136.5 \, \text{cm}^2$

Since there are two triangular faces:

$\text{Total area of both triangular faces} = 2 \times 136.5 \, \text{cm}^2 = 273 \, \text{cm}^2$

Step 3: Area of the rectangular faces

There are three rectangular faces, and their areas are calculated as follows:

1. Face 1 (connected to the base of the triangle):

   • Dimensions: $13 \, \text{cm} \times 35 \, \text{cm}$
   • Area = $13 \times 35 = 455 \, \text{cm}^2$

2. Face 2 (connected to the height of the triangle):

   • Dimensions: $21 \, \text{cm} \times 35 \, \text{cm}$
   • Area = $21 \times 35 = 735 \, \text{cm}^2$

3. Face 3 (the hypotenuse of the triangle):

   • To find the hypotenuse, use the Pythagorean theorem: $\text{Hypotenuse} = \sqrt{13^2 + 21^2} = \sqrt{169 + 441} = \sqrt{610} \approx 24.7 \, \text{cm}$
   • Dimensions: $24.7 \, \text{cm} \times 35 \, \text{cm}$
   • Area = $24.7 \times 35 = 864.5 \, \text{cm}^2$

Step 4: Total Surface Area

Add up all the areas:

$\text{Total Surface Area} = 273 \, \text{cm}^2 + 455 \, \text{cm}^2 + 735 \, \text{cm}^2 + 864.5 \, \text{cm}^2 = 2327.5 \, \text{cm}^2$

Step 5: Round to 3 Significant Figures

Rounding $2327.5 \, \text{cm}^2$ to three significant figures:

$\text{Surface Area} = 2330 \, \text{cm}^2$

The surface area of the solid is 2330 cm².

Would you like more details or have any questions?

Here are five relative questions for further practice:

1. How would the surface area change if the length of the prism were doubled?
2. What would the surface area be if the height of the triangle was increased by 50%?
3. How do you calculate the volume of this triangular prism?
4. How does the hypotenuse affect the surface area?
5. What other methods can be used to find the surface area of complex solids?

Tip: Always double-check your significant figures when presenting final answers in exams or reports.