$$200\times \left( 1-\frac{1}{10}-\frac{1}{5}-25 \textbackslash\% -15 \textbackslash\% ~\right)=60$$. 
The possible grades on an exam are $$5$$, $$4$$, $$3$$, $$2$$, or $$1$$. In a class of $$200$$ students, $$\frac{1}{10}$$ of them got $$5$$s, $$\frac{1}{5}$$ them got $$4$$s, $$25 \textbackslash\% $$ of them got $$3$$s, and $$15 \textbackslash\%$$ of them got $$2$$s. How many students got $$1$$s ? 
a. $$40$$ 
b. $$60$$ 
c. $$80$$ 
d. $$100$$ 