Not including tax, a total of 19 pens and markers cost $11.50. The pens cost $0.25 each, and the markers cost $0.75 each. Write the system of equations that could be used to solve for the number of pens, p, and the number of markers, m, bought.

To set up the system of equations, we can establish two equations based on the information provided.

1. The first equation is based on the total number of pens and markers:
\[
p + m = 19
\]

2. The second equation is based on the total cost of the pens and markers:
\[
0.25p + 0.75m = 11.50
\]

So, the complete system of equations is:

\[
\begin{align*}
1. & \quad p + m = 19 \\
2. & \quad 0.25p + 0.75m = 11.50
\end{align*}
\]

___p + _______m =_______

To express the equations in the requested format with blanks filled in, we can rewrite both equations:

1. For the number of pens and markers:
\[
1p + 1m = 19
\]

So, it can be filled in as:
\- **1**p + **1**m = **19**

2. For the total cost of pens and markers, we can eliminate the decimals by multiplying the entire equation by 100:
\[
25p + 75m = 1150
\]

So, it can be filled in as:
\- **25**p + **75**m = **1150**

Thus, your response would be:
- For the first equation: **1**p + **1**m = **19**
- For the second equation: **25**p + **75**m = **1150**