Answer :

MattD
Arrange ratio:

If the dog ate 12 muffins and this accounted for three-tenths of total how many muffins is a whole? Therefore, our ratio is as follows:

where 1 is a whole, and 3/10 = 0.3

12 ----------- 0.3
x ------------- 1

Multiply on the cross:

12 * 1 = 0.3 * x
0.3x = 12 |:0,3
x = 40

There are 40 muffins.