We plot the vertices of a triangle i.e., (0, 4), (0, 0) and (3, 0) on the paper shown as given below

Now, perimeter of ΔAOB = Sum of the length of all its sides:

Distance between the points

= Distance between A(0, 4) and O(0, 0) + Distance between O(0, 0) and B(3, 0)

+ Distance between A(0, 4) and B(3, 0)

Hence, the required perimeter of triangle is 12