It's a right triangle
if there is one 90°
Answer:
Decrease of 63.5%.
Step-by-step explanation:
Exponential function:
An exponential function has the following format:

In which y(0) is the initial value and r is the rate of change, as a decimal. If r is positive, it is a increase. If it is negative, it is a decrease.
In this question:
We have that:

So


So a decrease of 63.5%.
Based on the ratio of boys/girls We can infer that the only possibility for Ellen's math class would be answer B. 14/21