A researcher randomly surveyed seniors at a high school and asked how many books they read in the past year. The table shows the results.

Which statement is true?

8a-2

Step-by-step explanation:

The perimeter of a trapezoid is the addition of its four sides.

Perimeter of trapezoid= 39a – 7.

Length of 1st side= 9a,

Length of 2nd side= 5a + 1,

Length of third side= 17a – 6.

Length of the fourth side= Unknown

To find the length of the 4th side, we add the length of the three sides together and subtract from the perimeter of the trapezoid. This will be:

= 39a-7 - (9a+5a+1+17a-6)

= 39a-7-(9a+5a+17a+1-6)

= 39a-7-(31a-5)

=39a-7-31a+5

= 39a-31a-7+5

= 8a-2

The length of the 4th side is 8a-2