Help plz I don’t understand

In a small section of a stadium there are 40 spectators watching a game between the cook islands and fiji. they all support at least one of the two teams. 25 spectators support the cook islands and 16 of these support both teams. how many support only fiji?

Y+ 2/y is it a polynomial in one variable or not? and if so, why?

Which of the following questions describes the equation g + (-4) = -5? a)what number, when added to negative four, is equal to negative five? b)what number, when added to negative five, is equal to negative four? c)what number, when subtracted from negative four, is equal to negative five? d)what number, when subtracted from negative five, is equal to negative four?