What has 13 hearts but no other organs?

Can you replace the question mark with the correct number?

I have branches, but no fruit, trunk or leaves. What am I?

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

2, 3, 5, 9, 17, _ What is the next number in the sequence?

I live in a bowl. I can swim. I have a tail. I also have fins and big eyes. What am I?

I throw two dice simultaneously.

What is the probability of getting a sum as 9 of the two numbers shown?

A few friends are enjoying their sea voyage in a boat full of apples. On the way, they felt hungry and thus decided to eat the apples. Together, they ate two dozen of apples. When they have eaten the apples, will there be any change in the water level?

Place a mathematical symbol between the numerals 5 and 9 in such a way that the resulting number is greater than 5 but smaller than 9.

A girl was standing near the window thinking something. All of a sudden she decides something and throws something out of the window. She dies very soon after throwing it. She was perfectly healthy and had no disease or allergy. No one killed her and she did not commit suicide.

Can you think of any possible explanation that is logical as well for what happened there?