"Replacing Letters With Numbers to Find the Answers in a Grid" is a worksheet that encourages algebraic thinking by inviting students to find the values of the letters in a grid. Columns and rows of letters are added, subtracted, or multiplied, and the answer is listed on the outside of the grid. Simpler grids feature two rows of three, while more complex grids feature three rows of three. Each puzzle has one spot, either a square within the grid or an answer on the outside, that is replaced with a question mark for them to solve.

Each puzzle comes with equations and hints to help students find the answer. There is also a spot at the bottom where they can show their work as they figure out the values of each letter before solving the question mark.

Although students don't explicitly tackle algebra until middle school, younger elementary students are capable of exploring algebraic concepts once they have learned that they can solve addition problems using subtraction or subtraction problems by using addition.

Giving students simple equations with one of the numbers left blank is the easiest way to practice. One example would be _-4=3. Students can see how adding 4+3 equals 7, so the number 7 must go in the blank.

Puzzles are a fun way to practice, too. For example, each square of a grid can be filled in with the letters A, B, and C while the answers are listed on the right-hand and bottom side of each grid. With a few hints (like A+C=15) and room to show their work, students can figure out the values for each of the three letters.