let the 4 consecutive integers be x-1, x, x+1 and x+2, where x is integer

the first integer: x - 1

the thrid integer: x + 1

the sum of the first and the third is 84

x-1 + x + 1 = 84

2x = 84

x = 84/2

x = 42

x - 1 = 42 - 1 = 41 the first number

the numbers are: 41, 42, 43 and 44.