I think this is the Transitive postulate of equality.
Personally I can't see much point in giving labels to these equalities.
Answer:
$219.70
Step-by-step explanation:
First, you need to find the area of the certificate, which you can do by multiplying 10*13, since it is a rectangle. 10*13 is 130. Then, multiply 130 by the price per inch, which is $1.69. 130*1.69=219.7, which in financial terms would amount to $219.70.
Answer:
The temperature of the liquid 15 minutes later is 
Step-by-step explanation:
This is an example of arithmetic progression
We need to find 15 th term
Here

To get your answer, you will need to find the perpendicular slope for -1/3x which is just the opposite therefore it will be 3x. Your slope is 3x as perpendicular so use this slope to do point slope. Y-1=3(x-2). Distribute y-1=3x-6. Add 1 to both sides. (-1+1) (-6+1)=-5. So your equation in slope intercept form is y=3x-5. Going through the two points.
Hope this helps!