It's $0.44 cents my good friend......
Square (added characters)
Well, QR is the hypotenuse of the triangle and PT is another side of the triangle. You can use phythagoras theorem to work this out. So squareroot 13-8. That should give your your answer
In this sequence you are adding 4 to the previous number. That means that to find the next number, you will have to add 4. The next number is 21, the one after that is 25, the one after that is 29
