Answer:
The area of the triangle is of 21 units of area.
Step-by-step explanation:
The area of a triangle with three vertices
is given by the determinant of the following matrix:

In this question:
Vertices (3,0) (9,0) (7,6). So




The area of the triangle is of 21 units of area.
Answer:
6
Step-by-step explanation:
6 students play all three sports.
Answer:
15
Step-by-step explanation:
If CD and DE equal, then x+6 = 4x -21
So if you subtract x from both sides and plus 21 to both sides, that would be 3x = 27. Divide by 3 on both sides and you get 9.
Plug in x+6 with 9 and you get 15.
Answer:
10
Step-by-step explanation:
(3 + 12) - 3² + 8 · 2 ÷ 4
15 - 9 + 16 : 4
6 + 4
10