let, the number be "x"
Now,
according to the question,
4x -8 = x -23....................This is your equation.
Now solving it,
4x - 8 = x - 23
4x - x = -23 + 8
3x = -15
x = -15 / 3
x = -5
Checking the answer,
4 (-5) - 8 = (-5) - 23
-20 - 8 = -5 - 23
-28 = -28......................................true
