If the perimeter is known / given and is 6x, you can find the length of the unknown side by adding up the lengths of the other two sides and subtracting this sum from 6x:
6x - (x+3 + 2x + 4) = 6x - x - 3 - 2x - 4
Combining like terms, 3x - 7 represents the length of the unknown 3rd side.<span />
Pythagorean
Theorem as follows: A^2+B^2=C^2
777 divided by 21 = 34 with a remainder of 3
Answer:
BC~=AD (GIVEN )
CBA=CDA (altanate angles BC=AD)
C=A (altanate angles (BC=AD)
AAS
brainyliest please
Once you get to 0 that is the decimal