The sum of four consecutive integers is decreased by 30, the result is the fourth integer. Find the four integers.

First represent the unknowns with variables. Note that the difference between two consecutive integers is one, so:

Let x = first integer
Let x+1 = second integer
Let x+2 = third integer
Let x+3 = fourth integer
Then we set up the equation by following the given condition.
x + x+1 + x+2 + x+3 - 30 = x+3
Then solve for x:
4x + 6 - 30 = x + 3
4x - 24 = x + 3
4x - x = 24 + 3
3x = 27
x = 9 (first integer)
x+1 = 10 (second integer)
x+2 = 11 (third integer)
x+3 = 12 (fourth integer)

Hope this helps~ :3