Since this is a equilateral triangle all angles are equal to each other. All angles in a triangle always add up to 180 degrees.
So you would set up your equation like so
3(7x - 3) = 180
The 3 outside the parenthesis resembles the 3 angles.
You equal the equation to 180 since all the angles in a triangle = 180
So distribute the 3
21x - 9 = 180
Add 9 to both sides
21x = 189
Divide 21 on both sides
x = 9
The initial expression is:
So we can solve for r so:
Answer:
64/19
OR
3 7/19
depending on how you need to write it
Step-by-step explanation:
1) given
2) definition of an angle bisector
3) reflexive
4) 
(ASA)
5) 
(CPCTC)
Answer:
422 in.2
Step-by-step explanation:
Substitute the measurements of the rectangular prism into the formula SA = 2(lw) + 2 (lw) + 2(lh): 2(13)(7) + 2(6)(7) + 2(13)(6) = 422 in2.
