Striping numbers from a sum result

Question

I am trying to strip the first digit "if " the sum of two digits is a double digit. If there is a single digit I want the result to remain untouched.

Example : if I add the sum of 9 and 3 in the cells the normal result will be 12.
The desired outcome I am trying to formulate is the result will leave 2 instead of 12.

However I need a variable if the result of two cells is a single digit, lets sat we change the sum instead of 9, is 5 plus 3, which equals 8. Then the 8 is left unaltered.

It is a simple numerical text input and output, how ever the additional variable to strip the 1st digit "if 2 exist and replacement is not a mathematical formula.

Thank you in advance for looking at this problem I cannot seem to correctly formulate

Jerr