One gallon is equivalent to 128 fluid ounces
3 gallons is equivalent to 3*128 fluid ounces
= 384 fluid ounces
One plastic cup can hold 12 guide ounces
So cups needed will be 384/12
32 cups
X+x-17+39=180
2x+22=180
Subtract 22 from both sides
2x=158
X= 79
For this case we have that by definition, the equation of a line in the slope-intersection form is given by:

Where:
m: It is the slope of the line
b: It is the cut-off point with the y axis

We have the following points:

Substituting we have:

Thus, the equation is of the form:

We substitute one of the points and find "b":

Finally, the equation is of the form:

Answer:

20% = 0.20
800 * 1.20 = 960
total cost = £960