Here are five practice questions for solving systems of linear equations by substitution:

1. Solve the system of equations: $x + y = 5$ $2x - y = 4$

2. Solve the system of equations: $3x + 4y = 12$ $x - y = 1$

3. Solve the system of equations: $x = 2y + 3$ $4x - y = 10$

4. Solve the system of equations: $5x + 2y = 14$ $2x - y = 3$

5. Solve the system of equations: $x = 3y - 1$ $2x + 4y = 10$

Would you like to see the solutions or need clarification on any of these?

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Here are some follow-up questions you might find interesting:

1. How do you check the solution of a system of equations after solving it?
2. What happens if a system has no solution or infinite solutions?
3. How do you solve a system using the elimination method as an alternative to substitution?
4. Can substitution work with non-linear systems of equations?
5. What is the graphical interpretation of the solution to a system of linear equations?

Tip: Always solve for one variable first and then substitute it into the other equation to avoid dealing with complex expressions right away.