to get the cost of 1d, we have to get the 3 to change into a 1. the only way to do this is to divide 3 by 3. if we divided the left side by 3 we must also do the right so: 3d = 48 1d = 16
so 1 dozen = 16
to change 3d into 9d we have to multiply by 3. we again have to do this to both sides. so: 3d = 48 9d = 144
