15) A recycling factory makes its own new paper cups. It can make one new cup from nine used ones. If it has 515 used cups, how many new cups can it possibly make in total?

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The answer is (a) 12-2(-1)(6)2(6)=12

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