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!