Answer:

Step-by-step explanation:
<u><em>The picture of the question in the attached figure</em></u>
we know that
The perimeter of a triangle is the sum of the length of their three sides
so

where
a,b,c are the length sides of the triangle
In this problem we have

substitute and solve for the missing length

Answer:
it would be A:55%
Step-by-step explanation
For percent, to make it easier try to turn it into a 100.
20x5=100
do the same to the 9.
9x5=45.
Now subtract 45 from 100.
100-45=55.
There was a discount of 55%.
If you were to plot the function y=-x+6, both functions meet at the point (4,2)