Answer:
6.3
Step-by-step explanation:
If you cut a line through a rectangle diagonally, you form two right triangles. Since you have a right triangle, you can use the Pythagorean Theorem. The diagonal line will be the hypotenuse, and the width will be one of the legs.
a² + b² = c²
(3)² + b² = (7)²
9 + b² = 49
b² = 40
b = √40
b = 6.3
The length of the envelope is 6.3 inches.
