There are 4 quarters in 1 whole, just like there are 4 quarters in 1 dollar. In 3 wholes there are 3 times as many=12 just like you make up $3 with 12 quarters or, in arithmetic, 12/4=3. 3 divided by a quarter is 3/(1/4). To divide by a fraction, invert it and multiply. 1/4 inverted is 4/1=4 so 3*4=12.