A shop reduces the price of its dresses by 30%.
As a result it sells 60% more dresses than last month.
Calculate the percentage increase in its takings.
Let $\displaystyle n$ be the number of dresses.
x be the cost of the dress.
Last months takings was number of dresses multiplied by the cost of the dress which is $\displaystyle nx$
This month the dress has been lowered by $\displaystyle 30$% so $\displaystyle x$ is now $\displaystyle 0.7x$
And they sold $\displaystyle 60$% more so $\displaystyle n$ becomes $\displaystyle n(1 + 0.6)$
So the takings this month is $\displaystyle 1.6n$ multiplied by $\displaystyle 0.7x$ which is $\displaystyle 1.12nx$ which is a $\displaystyle 12$% increase.