Let's say a = number of ordered soups, b = number of ordered sandwiches.
Then 4.5a + 7.75b = 113.50, and a and b are integers between 0 and 18 inclusive.
How do we tackle this? If all ordered soup, the cost would be $81, so we'll have at least 4 sandwiches. If all ordered sandwich, the cost would be $139.5, so at most 15 sandwiches were ordered. You also know an even number of sandwiches was ordered, to let the price end at 50 cent.
If you brute-force from 4,6,8,10,12 to 14 sandwiches, you find the answer at 10 sandwiches and 8 soups.
10*7.75 + 8*4.50 = 113.50
ANSWER:

STEP-BY-STEP EXPLANATION:
We have that the equation in its slope-intercept form is the following:

The slope can be calculated as follows:

We use the points (4,7) and (1,1) to calculate the slope:

Now, we calculate the value of b, using the point (1,1) and the slope, like this:

Therefore, the equation would be:
Answer:
1,022.83 ft³
Step-by-step explanation:
volume= ⅓×½××19×17×19 = 1,022.83 ft³
Y=mx+b
b= -2
m= rise/run = 2/3
y=2/3x-2