If 4 did not exist, then you would be using a base-4 quarternary numbering system (which is able to use the numbers 0,1,2,3)
The system will be similar to how our base 10 numbers work, but instead of counting to 9 before adding a trailing zero and becoming 10, you would count to 3. So 2 plus 2 would roll past 3, and equal 10.
If 4 did not exist, then you would be using a base-4 quarternary numbering system (which is able to use the numbers 0,1,2,3)
The system will be similar to how our base 10 numbers work, but instead of counting to 9 before adding a trailing zero and becoming 10, you would count to 3. So 2 plus 2 would roll past 3, and equal 10.