Isolate the variable by adding, subtracting, multiplying or dividing on both sides of the equal sign. For example, you may wish to solve for "x" in the following equation: "5x + 2 = 2x + 17." Subtract "2x" from both sides to get the unknown on one side: "3x + 2 = 17." Then subtract two from both sides to get the numbers on one side: "3x = 15."
Solve for "x" by adding, subtracting, multiplying, or dividing to get the "x" by itself. From the example above, you can identify that three is a common factor on both sides of the equation "3x = 15" because 15 is divisible by three. To isolate the unknown variable, divide both sides by three to get the answer: "x = 5."
Check your work. If you've successfully solved for the unknown, you should be able to plug your answer in wherever the unknown is in the original equation. From the example above, "x = 5." If you input five for "x," you get "5(5) + 2 = 2(5) + 17." Calculate as is appropriate to reach the same number on both sides. For example: "5(5) + 2 = 2(5) + 17," which is "25 + 2 = 10 + 17," which is "27 = 27."