This problem presents an opportunity for students to think about patterns, units of measurement and also to work on expressing the pattern as a formula that will lead them to thinking algebraically.
If your state has adopted the Common Core State Standards, this alignment might be helpful:
Grade 6: Expressions & Equations
6.EE.6. Use variables to represent numbers and write expressions when solving a real-world or mathematical problem.
Grade 7: Expressions & Equations
Solve real-life and mathematical problems using numerical and algebraic expressions and
Grade 8: Expressions & Equations
8.EE.7. Solve linear equations in one variable.