The method to solve such problems is  THIS:


Make a square 6x6 table with two inputs:



    One input will be vertical column to the left of the table with the possible input values from 1 to 6 for the first dice.


    Another input will be horizontal row above the table with the possible input values from 1 to 6 for the second dice.



In the table (in its cells) put the sum of the values from both inputes.


Next, calculate how many cells in the table satisfy (meet) your criterion.


Then divide this amount by 36 (= the number of cells in the table), and you will get the required probability.