Books Read by Lily and Mark

Two friends, Lily and Mark, are studying the relationship between the number of books they read each month. Lily reads a total of $2x + 5$ books, while Mark reads $3x - 4$ books. They discovered that the total number of books read between them is $26$ during a particular month.

Set up a system of equations to determine the value of $x$. Solve for $x$ and provide your answer as a grid-in response.