The missing number is the constant of proportionality, which can be found with the following formula.
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]
Let's use the points (1,10) and (3,30). Now, we replace them in the formula.
[tex]m=\frac{30-10}{3-1}=\frac{20}{2}=10[/tex]
The constant of proportionality is 10.
Therefore, the missing number is 10.
