SAT · Heart of Algebra · Linear equations in one variable
Question sat-q-00003
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The question
If 5x + 10 = 55, what is the value of x?
- 9
- 8
- -9
- 10
Show answer & worked solution
Answer: 9
Worked solution. Subtract 10 from both sides: 5x = 45. Divide both sides by 5: x = 9.
Why each wrong choice is wrong. The off-by-one and negated answers are common arithmetic-slip distractors. Watch the sign of the constant term when you move it across the equals sign.
Test-day tactic. When the stem is short, do the algebra straight rather than plugging in answer choices — it's faster.
About this question type
These items present a linear equation in a single variable and ask you to solve for that variable. The variable may appear on both sides; the equation may include nested parentheses, fractional coefficients, or a variable in a denominator that turns out to cancel cleanly. The test occasionally hides a one-step equation inside a sentence-long word problem, where two-thirds of the difficulty is parsing the English.
You will see a question shaped like this one on roughly every other official SAT form, typically at a moderate position in the section — solidly within the range that separates a 600-band student from a 700-band student. Treat any miss in this subtopic as a signal to drill the subtopic page before you do another full practice test.