Answer: 
Step by step:

(Used a table of common angles)
Answer:
coefficent matrix
Step-by-step explanation:
P. 366
"If the column of constant terms is not included, the matrix reduces to that of the coefficent matrix of the system"
-1 -3 -1
9 -9 -1
-1 -3 4
You can do it this think and if you can't I will help you
Answer:
You can use the Side-Angle-Side Postulate.
Step-by-step explanation:
The Side-Angle-Side (or SAS) Postulate basically states that if two sides of two triangles and the included angle are congruent, the two triangles are congruent.