Well, I don't really understand if it is 30 or 305 because of the spacing but I'll answer both. If it is 5y+305, just divide the whole equation by 5 and it will look like this (5y+305) then the factor would be 5(y+61)
5
If it is 5y+30 it would be just in the same process, Divide the equation by 5 and the result will be 5(y+6).