1. b. false.
Translate information into simple real-world terms.
Wheat flakes: $2.50
Corn flakes (less than wheat): $2.00
Oat flakes (more than wheat): $2.75
You can see from the above, that oat flakes cost less than corn flakes is clearly false.
2. c. uncertain.
Write down the information you know and try to fill in what you don't.
Gloria: 12 years old
Francesca: 14 years old (older than Gloria)
Yvonne 13 years old (older than Gloria, but older than Francesca)
Yvonne 19 years old (older than Gloria, but younger than Francesca)
So the statement that Yvonne is older than Francesca is uncertain.