Of 3/1=6/2 then 3-1/1=

I'm not sure what you want with the first part (3/1=6/2)

well PEMDAS or parenthasees exponents, mult or division whichever comes first, addition subtraction, whichever comes first so

3-1/1 would be divison first
1/1=1
3-1=2

So don't take my word i'm not exactly a mathematical person but i would assume a. because while selling the soap every month you increase in sells so you would by 11 percent. the you would get the factor 0.89 which if i had to guess would be the monthly profit over 11 probably wrong tho