let "a number" = x
(x) + (x + 1) + (x + 2) = 72
Simplify. Combine like terms
3x + 3 = 72
Isolate the x. Note the equal sign. What you do to one side, you do to the other. Do the opposite of PEMDAS.
3x + 3 (-3) = 72 (-3)
3x = 72 - 3
3x = 69
3x/3 = 69/3
x = 69/3
x = 23
23 is the smallest number
hope this helps