Answer:
and 
Step-by-step explanation:
Coefficients are simply the numerical constants "attatched" (being multiplied by) [to] the variables.
Let t be the time in minutes for the GT-S50 to scan the manuscript, working alone.
Then the G7-1500 will take 2t minutes to scan the manuscript, working alone.
If both machines work together for 1 minute they will scan 1/5 of the manuscript.


2t = 15
t = 7.5
When working alone, the machines will take the following times to scan the manuscript:
G7-1500: 15 minutes, GT-S50: 7.5 minutes.
Answer:
Im not sure about it.
Step-by-step explanation:
First make the y on a side alone without anything by multiplying both sides by 2 then dividing by three, then substitute the x by the x value of x represented in the ordered pairs, and if the the result was the same value for y as represented in the ordered pair, then the ordered pair is correct.
Here's infinity minus 1.

If you don't like that, here's 1,153,300,781,250.

_____
Please note that according to the order of operations, the only denominator value is the first box after "÷".
Set x's equal
21x +35y = 7
21x + 12y = -39
Subtract from one another
23y = 46
Divide
y = 2
Hope this helps ;)