The relationship between the two variables can be determined as the slope, which is;
[tex]\begin{gathered} m=\frac{y2-y1}{x2-x1} \\ \text{Where;} \\ x1=3,x2=4,y1=15,y2=20 \\ m=\frac{20-15}{4-3} \\ m=\frac{5}{1} \\ m=5 \end{gathered}[/tex]This means for every ordered pair in the table, the books multiplied by 5 gives the cost.
Therefore the ordered pair that would be included in the table is (10, 50) which is option number 4.
