Let's denote the cost of each mechanical pencil as
Mr. Spears' total budget is $25. The cost for erasers can be expressed as the number of bundles of erasers multiplied by the price per eraser. Since erasers come in bundles of 10 and cost $0.50 each, if he buys
Now, if Mr. Spears spends part of his budget on erasers and the remaining part on mechanical pencils, we can express this as:
Adding the two costs together gives us the equation:
To compute the cost of each mechanical pencil in terms of the other variables, you can rearrange the equation for
Dividing both sides by
Here,