Hello!
So, we know that the length of the rectangular basketball court is 84 ft, and the width is 50 ft. 
The formula for perimeter of a rectangle is: 
P = 2l + 2w
This means that we need to multiply the length by two and the width by two as well. 
Substitute: 
P = 2(84) + 2(50)
P = 168 + 100 
P = 268 ft 
ANSWER: 
The perimeter of the basketball court is 268 feet long.