I think the answer is 20 but I am not sure,I heard about 15 and 25
You can improve your drawing skills by practicing more and little by little, you can get better at it.
I hope this helps :)
Answer: Music helped children learn the principles of mathematics, another key area of ancient Greek education. The philosopher Pythagoras realised the importance of harmonics and how music related to mathematics when he heard blacksmiths hammering in their forge, so the legend goes.
Explanation: hope this helps you! <3