## Thinking Mathematically (6th Edition)

Consider the equation for the condition at which the toll for the bridge with discount pass is equal to the toll for the bridge without discount $5x=30+3.50x$ Here, x is the number of times in a month the bridge must be used Now, solve the above equation \begin{align} & 5x=30+3.50x \\ & 5x-3.50x=30 \\ & 1.5x=30 \\ & x=20 \end{align} Thus, the number of times in a month the bridge must be used is 20.