21.5.......:::..............:.::.::..
Answer:
Area of triangle is 25.
Step-by-step explanation:
We have been given an isosceles right triangle
Isosceles triangle is the triangle having two sides equal.
Figure is shown in attachment
By Pythagoras theorem

AD is altitude which divides the triangle into two parts
DC=5 implies BC =10 since D equally divides BC
Let AC=a implies AB=a being Isosceles
On substituting the values in the Pythagoras theorem:




WE can find area of right triangle by considering height AB and AD
Area of triangle ABC is:
(1)

And other method of area of triangle is:
(2)
Equating (1) and (2) we get:



Using area of triangle is: 
Now, the area of triangle ABC=

Answer:
Yes
Step-by-step explanation:
It is true because the equation would be 1 is less than or equal to 3-(-4)
Answer: The correct answer is "No, because there is a lot of variability in the language arts book data."
The mean of the language arts book is higher than the mean of the social studies book, however, there is a lot of variability in the language arts book. This means that the language arts book could actually be lower than the social studies book. It is not likely but it could happen.