Final answer:
The width of the rectangular swimming pool is 14 yards.
Step-by-step explanation:
To find the width of the rectangular swimming pool, we can use the formula for the perimeter of a rectangle, which is P = 2(length + width). Given that the perimeter is 70 yards and the length is 21 yards, we can rearrange the formula to solve for the width:
P = 2(21 + w)
70 = 2(21 + w)
Divide both sides by 2:
35 = 21 + w
Subtract 21 from both sides:
14 = w
Therefore, the width of the swimming pool is 14 yards.