The distance between two points is given by:
[tex]d(A,B)=\sqrt[]{(x_2-x_1)^2+(y_2-y_1)^2}[/tex]Then, in our case, we have:
[tex]\begin{gathered} d(A,B)=\sqrt[]{(6-3)^2+(15-12)^2} \\ =\sqrt[]{(3)^2+(3)^2} \\ =\sqrt[]{9+9} \\ =\sqrt[]{18} \\ =4.2426 \end{gathered}[/tex]Therefore the distance between the points (rounded to the nearest whole number) is 4.