Well idk about geometric theorem or how ever. but, because they have the same line aka the same Slope. The other line is parallel to it. Assuming by the statement, -1/3x has another -1/3x of the same Slope.
Let the colored pencil amount be p.
Then this is the equation:
12p+p=78
Simplifying, we can see that
13p=78
Divide both sides by 13 to get
p=6
Since there are 12 times as many markers as colored pencils, there are 72 markers.
