Answer:

Step-by-step explanation:
<u>Equation of the line</u>
A line can be expressed in many forms.
The equation of the line in slope-intercept form is:
y=mx+b
Being m the slope and b the y-intercept.
The point-slope form of the equation of a line is:
y-k=m(x-h)
Where m is the slope and (h,k) is a point through which the line passes.
The equation of a line passing through points (x1,y1) and (x2,y2) can be found as follows:

We are required to find a line with slope m=4 passing through the origin (0,0).
Using the point-slope form:
y-0=4(x-0)
Simplifying

Step-by-step explanation:
You have 120 bottles of Cola and 120 bottles of Sprite.
You can exchange 3 empty Cola bottles for a new bottle of Sprite.
You can exchange 4 empty Sprite bottles for a new bottle of Cola.
You can borrow empty bottles, but must return them in the end.
What is the maximal number of bottles of drink that you can drink? Prove the optimality of your result.
As this is a puzzle, please give short and clever answers rather than tedious bruteforce calculations.