Answer: n = 31
Explanation: Remember that the word sum mean addition.
So the sum of twice a number and 13 means 2n + 13 = 75.
So our equation is 2n + 13 = 75.
Now let's solve the equation.
Start by subtracting 13 from both sides to get 2n = 62.
Now, divide both sides by 2 and we have n = 31.