We have learnt that to evaluate the value of an algebraic expression, we substitute a value of the variable in the given expression. Consider Example 3, where the wire is bent to form a rectangle. Here, the area of the rectangle, $10x - x^2$, is a function of $x$. Can you interpret this as an input-output process? What value does the expression take when $x = 6$ cm?                                                                                                                                                [Page No. 20]