Question

One pen costs $Rs15$ and one pencil costs $Rs3$. What is the total cost of $x$ pens and $y$ pencils

Answer 1

Cost of one pen $=Rs.15$

Cost of $x$ pens $=15\times x=Rs.15x$

Cost of $1$ pencil $=Rs.3$

Cost of $y$ pencils $=3\times y=3y$

Therefore,

Total cost of $x$ pens and $y$ pencils $=15x+3y=3(5x+y)$