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

• A. $x+5=12$
• B. $x^2=25$
• C. $y+z=10$
• D. $x-3<7$

Answer: (A)

Verified step by step guidance

1. Recall that a linear equation in one variable is an equation that can be written in the form \(ax + b = 0\), where \(a\) and \(b\) are constants and \(x\) is the variable raised only to the first power.
2. Examine each given option to identify if it fits the form of a linear equation in one variable:
3. 1. \(x + 5 = 12\) has one variable \(x\) raised to the first power and constants on both sides, so it fits the linear form.
4. 2. \(x^2 = 25\) has the variable \(x\) raised to the second power, which makes it a quadratic equation, not linear.
5. 3. \(y + z = 10\) has two variables, \(y\) and \(z\), so it is not an equation in one variable.
6. 4. \(x - 3 < 7\) is an inequality, not an equation, so it does not qualify as a linear equation.