Which of the following is a linear equation in one variable?

• A. $x+5=12$
• B. $x^2=25$
• C. $y+z=10$
• D.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand what a linear equation in one variable means. A linear equation in one variable is an equation where the variable is raised only to the first power (no exponents other than 1), and there is only one variable present.
2. Step 2: Examine each given equation to identify the number of variables and the powers of the variables.
3. Step 3: For the equation \(x + 5 = 12\), note that there is only one variable \(x\), and it is to the first power, so this fits the definition of a linear equation in one variable.
4. Step 4: For the equation \(x^2 = 25\), the variable \(x\) is squared (raised to the power of 2), so this is not a linear equation.
5. Step 5: For the equation \(y + z = 10\), there are two variables (\(y\) and \(z\)), so it is not an equation in one variable. Similarly, \(x - 3 < 7\) is an inequality, not an equation.