Question

STAMPS For Exercises 39 and 40, use the following information.

The table shows the price for first-class stamps since the U.S. Postal Service was created on July 1, 1971.

39. Write a prediction equation for this relationship.

Short answer

The predictive equation of the given graph is $7y-15x=21.$

Step-by-step solution

Step-1 – Concept of solving two equations by graphing

To graph of a linear inequality in two variables$\left(xandy\right)$, first get $y$alone on one side. Then consider the related equation obtained by changing the inequality sign to an equality sign. The graph of this equation is a line. If the inequality is strict $\left(<or>\right)$ graph dashed line.

Step-2 –Draw the given graph

Step-3 –Write the equation of the graph

Here let$x=$age of U.S Postal stamp (years).

$y=$Price of U.S stamp (first class).

When $\begin{array}{l}x=3,y=3\\ x=10,y=18\end{array}$

$\begin{array}{l}y-3=\frac{18-3}{10-3}(x-0)\\ y-3=\frac{15}{7}x\\ 7y-21=15x\\ 7y-15x=21\end{array}$