Answer:
P =
units
A = 24.5 
Step-by-step explanation:
Length of one side
sin
= 
7sin
= x
7(
)= x
= x
Perimeter = 4(
) = 
Area = (
)(
) =
=24.5
Answer: -7
Step-by-step explanation:
Just plug in -2 for x:

This is an odd question because it's a little subjective, but, for me, I would choose x from the second equation because you could simply add 12y to both sides, then divide by 3. It has the added benefit of not having any decimals/fractions, or negative values, which would be nice for substitution.