The best way could be to use an array and store the answers. If it's always going to be numbers then you don't need to store the numbers and instead use the row number of the array as the number with the answer stored. If the question is going to be eventually something other than a number then yes store question and answer using two columns.
To pick the random number you would generate using something like floor(random(100)) which picks a random number from 1 - 100, then grab the expected answer from array position - array.at(num) where num is the number you just generated. So if the number is 18, array.at(18) picks the answer from row 18. If you stored both the question and answer then you'll need to also pick the column so array.at(num,0) is question and array.at(num,1) is the answer.