Alright, first let's make a variable for the number. 'n' Pretty easy right? Now, we know that the equation contains the sum of n and 3. n + 3 Since 35 is 9 more than the sum of n and 3: (n + 3) + 9 = 35 Great! Now we have the equation! We can open the parentheses and add 9 and 3 n + 12 = 35 Subtract both sides by 12: n = 23 The unknown number is 23!