maybe u want to ask" What is the tree?" or " Where is the tree?"

Ok, I think you mean "what are the three mistakes in this question?" Therefore, the three mistakes are: 1. Include "the" ("What are THE...) 2. "three" instead of "tree" 3. MistakeS is plural.

what is a tip???? what are the three mistakes in this sentence?

what are the three mistakes in this sentence?

"tree" should be "three".... am I right? by using "three", your 'mistake' must be "mistakes" :)