Can someone tell me what the difference between the less than or less than or equal to sigh and the greater than or greater than or equal to sign is

Ammonia molecules have three hydrogen atoms and one nitrogen atom. how many of each atom arein five molecules of ammonia

The reflexive property of congruence lets you say that ∠pqr ≅

Apasta salad was chilled in the refrigerator at 35° f overnight for 9 hours. the temperature of the pasta dish dropped from 86° f to 38° f. what was the average rate of cooling per hour?