lets call them
a, b, c
we know that
a+b+c=78
and we know they are consecutive which makes this problem a lot more easier
the number just after another number is that number plus one. example:
the number just after 3 is
3+1...which is 4
lets write our consecutive numbers in a way that we can use this principle:
a, a+1, a+2
a+a+1+a+2=78
3a+3=78
3a=75
a=25
the smallest number is 25