Answer: the width of the letter envelope is 100 mm.

Step-by-step explanation:To find the width of the letter envelope, we need to consider that the perimeter of a rectangle is given by the sum of all its sides.

Let's assume the length of the envelope is 150 mm. The perimeter is given as 500 mm.

The perimeter of a rectangle can be calculated as follows:

Perimeter = 2 * (Length + Width)

Substituting the given values:

500 = 2 * (150 + Width)

Dividing both sides by 2:

250 = 150 + Width

Now, let's isolate the width by subtracting 150 from both sides:

Width = 250 - 150

Width = 100 mm

Therefore, the width of the letter envelope is 100 mm.

Answer:

The width of the letter envelope is 100 mm.

Step-by-step explanation:

Let's denote the width of the letter envelope as "w" in millimeters (mm).

The perimeter of a rectangle can be calculated using the formula:

Perimeter = 2 * (length + width)

Given that the length of the envelope is 150 mm and the perimeter is 500 mm, we can set up the equation:

500 mm = 2 * (150 mm + w)

Simplifying the equation:

500 mm = 300 mm + 2w

Subtracting 300 mm from both sides:

200 mm = 2w

Dividing both sides by 2:

w = 100 mm