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 where the variable is raised only to the first power and appears in a form like \(ax + b = c\), where \(a\), \(b\), and \(c\) are constants.
2. Look at each option and identify the variable and its exponent or form:
3. For \(x + 5 = 12\), the variable \(x\) is to the first power, and the equation fits the form \(ax + b = c\).
4. For \(x^2 = 25\), the variable \(x\) is squared (raised to the second power), so this is not linear.
5. For \(y + z = 10\), there are two variables, so it is not an equation in one variable.
6. For \(x - 3 < 7\), this is an inequality, not an equation, so it does not qualify as a linear equation in one variable.