You are cutting wood into equally sized pieces so if you know the length of the wood and the size of the cuts...
That would be...
2/3 ÷ 2/15 = 2/3 x 15/2 = 5 pieces
For this case we have that by definition, the equation of a line in the slope-intersection form is given by:

Where:
m: It's the slope
b: It is the cut-off point with the y axis

We have the following points:

Substituting the values:
Thus, the line is of the form:

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

Finally we have to:

Answer:
The equation es 
2(2.5-(5/6))
2(1 2/3)
3 1/3