Variables, or unknown values, appear in numerous types of equations from simple algebra problems to complex calculus problems. But for the equation: 13m=12–m, you need to use PEMDAS. It stands for Parentheses, Exponents, Multiplication, Division, Addition, and Subtraction. Although, you could be able to do this yourself, I will do it for you. First, you add m to both sides. Then, you simplify. Then, divide both sides by 14. Then lastly, simplify. Your answer would then be: m=6/7