There are 12 bottles on the shelf but eh shelf can hold 20, how many more bottles do I need? Well you could draw a picture of 12 bottles to help you and keep drawing more until you get to 20. Or you could put 12 in your head and use your fingers to count on to 20 (12 + __=20). Also, you could work backwards and do 20-12. The answer is 8.
I have 20 ice cubes and I used 6 so how many are left. Again you could draw a picture and cross out the 6 ice cubes or you could do 20-6 and put 20 in your head and count back 6. The answer is 14.
