213+313 is same as
133+1
213+313
= 73+103
= 73+(73+1)
We know that if we take any positive number and add the next number, or if we double the first number and add 1, we get the same number as the result.
So,
73+(73+1)=273+1
So, 213+313
= 73+(73+1)
= 273+1
= 133+1