Let
X = {5, 10, 15, 20, 25, 30, 35, 40}.
Define a relation

on X as follows. For
a, b is in X,

a

b
if b can be obtained from a by adding a (possibly empty) collection of dimes (10 cents) and quarters (25 cents). So, for example,
25

35, but 25

30.

Give a pair of incomparable elements in
(X,

).
(Enter your answers as a comma-separated list.)

Question

Let 
X = {5, 10, 15, 20, 25, 30, 35, 40}.
 Define a relation 

 on X as follows. For 
a, b is in X,
 
a 

 b
 if b can be obtained from a by adding a (possibly empty) collection of dimes (10 cents) and quarters (25 cents). So, for example, 
25 

 35, but 25 

 30.


Give a pair of incomparable elements in 
(X, 

).
(Enter your answers as a comma-separated list.)

anonymous · Answer

they are common because its by 5's