We have the relation:
[tex]r=\frac{2}{5}t[/tex]
where r is the cups of red paint and t is the total cups of paint.
It is a proportional relationship, as r/t is constant.
We know that the point (0,0) belongs to the line, as when t=0, r is 0 too.
We can find another point by assigning a value to t and calculate for r.
For example, for t=10, we have:
[tex]r(10)=\frac{2}{5}\cdot10=\frac{20}{5}=4[/tex]
Then, the point (t,r) = (10,4) belongs to the line.
With 2 points we can graph the line as:
