Asingles tennis court is a rectangle 27 feet wide and 78 feet long. suppose a player at corner a hits the ball to her opponent in the diagonally opposite corner b. approximately how far does the ball travel, to the nearest tenth of a foot?

Basically, you just have to find the length of the rectangle that is 27 x 78 feet.
The equation for the diagonal: 
d = sqrt(l^2+w^2)
l = 27
w = 78
plug them in and solve
d = sqrt ( (27^2) + (78^2) )
d = sqrt ( 729 + 6084 )
d = sqrt ( 6813 )
d ≈ 82.5

The ball traveled approximately 82.5 feet from one corner of the rectangular 27 x 78 foot field, diagonally to the other side.

Hope this helps

Idon't know that language