Let the unknown number be y.
We can list the equation out by the clues given.
5y + 12 = 52
Then solve this as simple algebra!
Shift +12 to the other side and be - 12
5y = 52-12
5y = 40
Shift x5 to the other side and be ÷5
y = 40 / 5
y = 8
Therfore the unknown number is 8.
