could anyone help me with this question?

simmonaUID: 2199129

sorry i cannot type chinese at school, please help me with this problem, i have already spent a long time on it, thanks

x 0     1   2   3   4  5
y 25  24 22 16   8  0

x,y are two variables shown above,
calculate the slope of the relationship between x adn y when x =3

wpjcounterUID: 2229815

sorry but as for a dishbird like me ,"slope"is still an indifferent word for me