To find the total cost for purchasing \( x \) ink cartridges, you can use the given information:
1. Each ink cartridge costs $19.
2. There is a flat shipping charge of $7.50.
To express the total cost \( C \) as an algebraic expression for \( x \) cartridges, you can sum the cost of the cartridges and the flat shipping charge.
The cost of \( x \) cartridges is given by \( 19x \).
Therefore, the total cost \( C \) can be written as:
\[
C = 19x + 7.50
\]
This expression represents the total cost for an order of \( x \) ink cartridges.