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:

So, let's set this up:
0.04x+0.05y=1100
0.05x+0.04y=1150
Let's multiply each equation by 100:
4x+5y=110000
5x+4y=115000
Now let's add those together:
9x+9y=225000
And we need to find x+y, so we just divide by 9 and get 25,000
To find how many bottles are plastic just divide 12 by 3. 12/3=4 so 4 is one third of 12.
total length of the boards = 4 1/2 meters
Given:
number of boards = 5
length of each board = 9/10 meters
5 * 9/10 = (5*9)/10 = 45/10
Simplify fraction:
45/10 = 4 5/10 or 4 1/2 meters.