The answer would be the 3rd one, (x | x &It; -3) hope this helps.
You want to find y so it should start with y=
then the next piece that is unknown is the number of months, but you know there are 3 new ones each month so you know you have to have 3x so you have y=3x
and then you can't forget to keep the original 25 on the team so y=3x+25