Need help!!request: plz help

See 2 me its a serious thing.umm....i hav recently joind my maths tution classes where other girls of my class also study.i was doing pretty well.1 dia our sir gave us assignment on algebra.1 of d sum was vry hard even sir cant solve it i actually did d sum wit d help of my dad & wen he saw my copy he asked me 2 explain d sum & i cud'nt.my sir said i must hav taken sum1's help.for tis i think d other gals & sir hav started thinking i m brainless & all other sums were also done por my dad & tis not true,i hav done sums on my own.so hw 2 mak'em understand that i m not a bad sort of a gal 2 do al sums frm my dad.jst tel me hw 2 get out of tis