What does SF stand for

Tina practice piano for 15 hours last month and 45 hours this month use multiplication to write a statement comparing me i was tina practice during the two months use addition to write a statement comparing the hours tina practice during the two months

The jewelry store is having a sale. necklaces that were regularly priced at $23.50 are on sale for $18.80. what is the percentage of decrease in the price of necklaces?

The paint recipe also calls for 1/4 cup of food coloring. tyler says mrs.mcglashan will also need 6 cups of food coloring. do u agree or disagree? explain.