Answer:
4
Explanation:
Addition is grouping things together and counting the total.
1 is simply 1. Think of 1 stick, I
3 is 3 sticks: III
Now put them together: I and III or simply IIII.
Count the number of stick in III.
There are 4 sticks, so 3 + 1 = 4
I hope this relives your anxiety.