If we write the first integer as the variable n, all numbers that come after it can be written as n+1, n+2, etc.
so the sum of four consecutive integers is:
sum = n + (n+1) + (n+2) + (n+3)
if we simplify:
sum = 4n +6
and if we want to know what the first integer is, we can re-write the equation as:
= n
and that is your answer.