Given:
Last year 80 students signed up for a summer trip to Washington, D.C.
This summer 50 students have signed up to go.
To find:
The percent decrease in the number of students.
Solution:
We have,
Students in last year = 80
Students in this year = 50
Now,





Therefore, the correct option is B.
Step-by-step explanation:

GIVEN:
We are given a parallelogram WXYZ with diagonals WY and XZ.
Required;
Prove that XZ bisects WY.
Explanation;
From the diagram provided, we can draw the following conclusion;

Also, we have;
The first step is to quickly factor each of the five equations... to do so, find the right factors of the 3rd given number so that they add up in an equal number to the second number... 14 = -7 • -2 and -9 = -7 + -2
a^2 - 9a + 14 = 0
(a - 7) (a - 2)
a - 7 = 0, a = 7
a - 2 = 0, a = 2
{2,7}
a^2 + 9a + 14 = 0
(a + 7) (a + 2)
a + 7 = 0, a = -7
a + 2 = 0, a = -2
{-2, -7}
a^2 + 3a - 10 = 0
(a + 5) (a - 2)
a + 5 = 0, a = -5
a - 2 = 0, a = 2
{-5, 2}
a^2 - 5a - 14 = 0
(a - 7) (a + 2)
a - 7 = 0, a = 7
a + 2 = 0, a = -2
{-2, 7}