Good mathematics book for class 6 and 7 are:-
1. R.S.Aggarwal's books of maths
2. R.D.Sharma's book of maths
3. srijan- maths booster
if you want to your parents to bring you an iphone, then first prove yourself to them. you show them you are concentrating in studies. you will use your mobile carefully for good things, not waste your time in it and it is not going to bother your studies.you also show them you need that iphone very much, if really. so you show them these, and there are more chances of getting an iphone. but don't ask for it for your own fun. and if it will ruin your studies, then forget it.