In a school hall in Nagpur, every row has the same number of chairs, p. There are also chairs on the stage, as shown. Which expression gives the total number of chairs?

To evaluate an expression, **substitute** a value for the variable and compute. If $x=5$, then $2x+3$ becomes $2\times 5+3=10+3=13$. The same expression with $x=0$ gives $2\times 0+3=3$. Practise substituting — it is the bridge between an algebraic expression and a real number.