Well if you don't know what the numbers are then you can let x be an even number, then your consecutive numbers would be x, x+2, x+4,x+6 etc. so lets say that x is an even number and you are told that x and the three consecutive even numbers after it added together equals 48. then you would say:
x + (x +2) + (x + 4) + (x + 6) = 48 combine like terms and you get:
4x + 12 = 48 subtract 12 from both sides
4x = 36
x = 9
and there you have it. Hope this helps :)