Students need to know what they’re in for. Thus, teaching missing numbers in elementary algebra requires an understanding of different topics. For example, tell them about algebraic quantities like variables, real numbers, constants and complex numbers. Students should also know that they are completing the same type of basic math used in lower-level math classes like multiplication, addition and subtraction.
Refamiliarize students with basic math to increase students’ confidence on working with missing numbers. One way to bridge the gap between what students learned in the past to elementary algebra involves asking students to solve a basic problem. Write the problem on the board with the answer missing. For instance, write “two multiplied by five equals x.” Ask students to answer the question. You want students to understand that they've seen algebra problems with missing numbers before so they aren't confused when they see the x in another place.
Teaching elementary algebra problem that has an x in the problem instead of the answer is similar to answering a linear equation. However, you must explain that you have to undo whatever was done to the variable. To undo what was done to the variable means isolating the variable or finding the number they’re looking for. When building on the linear math problem, you want to explain that you’re completing more steps to find the answer to the problem. Instead of finding out the answer, you have to conduct an investigation to uncover why the answer is there.
Write a problem on the board with the answer and one missing number. You can use the problem x + 6= -3 as Purplemath.com uses. Show students how to work the problem to get x on the same side as the equal sign. The students know that six was added to the missing number to get a negative three answer. Thus, you must show them how to undo the addition of the six. Stress to the students that whatever you do to one side of the problem, you have to do to the other side. For example, place a negative six underneath the positive six and the negative three. Subtract. The students should see the answer of zero on one side and negative nine on the equal side of the problem.