The equation 2X + 100 = 700 is a linear equation in one variable, where X represents an unknown value. To solve for X, we need to isolate it on one side of the equation. This involves performing operations that maintain the equality, such as subtracting 100 from both sides. After subtracting 100, the equation simplifies to 2X = 600. Next, we divide both sides by 2 to find the value of X. This results in X = 300, which is the solution to the equation.