To write an algebraic expression that describes the total cost for a single order of \( x \) cartridges based on the hint provided, we can break it down as follows:
From the hint, it seems that the first part of the total cost is 19 times 1 (which likely represents a base fee or charge), and the second part is an additional cost of $7.50.
If we assume that each cartridge costs $19 and there is also a flat fee of $7.50 for processing or shipping, then the cost for \( x \) cartridges can be calculated as:
- Cost of \( x \) cartridges: \( 19x \)
- Flat fee: \( 7.50 \)
Thus, the total cost \( C \) for an order of \( x \) cartridges can be expressed as:
\[ C = 19x + 7.50 \]
This expression gives the total cost for ordering \( x \) cartridges including any fixed fees.