let’s suppose he wants an average ability in these instruments

If you have the passion to learn these instruments, you can learn relatively fast to become of average ability . . . AND you’ll want to play more than 3 hours because of that passion.

I was 29 when I started to learn percussion; albeit, I was in L.A. and had great connections so had some highly qualified teachers, but it was up to me to practice and practice and I would practice 5 hours a day – if it was at night, I would just practice my timing with my LED Metranome, if neighbors were at work, I’d play hard with and without music.

8 months after starting (and congas, timbales and all the "ear candy" isn’t that easy to pick up so fast unless you are really passionate about it), I was in Europe with a band. First time out of the country. I CAN say I wasn’t the best percussionist, but my timing was perfect and I played all the "extras" this particular band wanted.

It all depends on the passion and love for the instrument(s) and music.

I have some names, piano, guitar, drums, cello, violin..just that,

please answer, from the easiest to the hardest one..thanks..
i did not mean anything by asking this question, just wanna know..what s wrong wit that??

Violin, cello, piano, guitar, drums. Violin is one of the hardest instruments to sound well. Having said this, some find violin easier than the guitar and this is determined by how much you love the instrument. I found guitar and piano easy. Then again, others may find it hard.