a piece of cake you cant eat
A piece of cake you can't eat is a lie told by someone who just bit into a cake that was in the trash.
You said the math was simple. I failed the quiz. You said you'd take the blame. You ran away.
He said the project was easy. It took me three days. He said he'd help. He took a nap.
She said the cake was fresh. It was moldy and tasted like regret.