5*9=45 right a comparison sentence that represents this equation

Suppose that John has a pen that costs $5 and he has 9 similar pens. The total cost of the pens that John has is equal to the cost of his bag. If the cost of the bag is $45, write the verbal model of the situation.

So, cost of each pen = 5

Number of pens = 9

Total cost = 5 * 9

But, it is given that the total cost = cost of the bag and

cost of the bag = 45

So, total cost = 45 and

5 * 9 = 45.