There are $$60$$ pupils in Arnold\textquotesingle s class. $$35$$ pupils like Maths and $$38$$ pupils like English. Twice as many pupils like both subjects as those that like neither of them. How many pupils like only Maths? 
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Let the number of pupils who like neither subject be $$x$$. Hence the number who like both subjects is $$2x$$. Therefore the number of pupils who like only Maths is $$35−2x$$ and the number who like only English is $$38−2x$$.  Since there are $$60$$ pupils in Arnold\textquotesingle s class, we have:  $$\left( 35-2x \right)+2x+\left( 38-2x \right)+x=60$$ and hence $$x = 13$$ and hence the number of pupils who like only Maths is $$35-(2\times 13)=9$$. 