Is there a picture for the problem?
Answer:
20x + 42y
Step-by-step explanation:
Answer:
Purple line: 4
Red dashed line: 2
Blue line: 1/2
Step-by-step explanation:
The purple line is the steepest line, therefore it has the biggest constant of proportionality or slope. Since 4 is the biggest number among the others, we attribute it to the purple line (the one with the point C on it).
Think of it this way:

here
so 
The greater a is, the greater y is. So for any value of x, y will be become bigger and bigger if we increase the value of a.
Take for example this one:

Take
therefore
Now take
and take
therefore
When we increased this constant of proportionality, as you can see from 2 to 4, the value of y increase from 4 to 8.
Hope this is helpful. Think of it really carefully, and I'm sure you'll grasp the concept.
Answer:
<h3>y = ¾x - 3</h3>
Explanation:
−3x + 4y = −12
<em>Add 3x to both sides</em>
−3x + 4y + 3x = −12 + 3x
4y = 3x − 12
<em>Divide both sides by 4</em>
4y / 4 = 3x − 12 / 4
<em>Simplify</em>