let x, x+1,x+2, x +3 are the numbers
so
x + x +1 + x +2 +x +3 = 198
4x + 6 = 198
4x =198-6
4x = 192
x = 192/4
x = 48
x + 1 = 48 + 1 = 49
x + 2 = 48 + 2 = 50
x + 3 = 48 + 3 = 51
proof
48 + 49 + 50 + 51 = 198
so the numbers are 48, 49, 50, 51
fourth number in this sequence is 51
