Explanation

The word "is" here is like an equal sign in a word, so we can express this question in algebra as



More precisely, "what percent" must be expressed as a decimal, or as a number over 100. Since the answer choices are expressed as percents (with a percent sign), the latter route is better for this question, so the accurate expression is







This sounds like an awfully high percent, but it's correct: 180 is nine times as big as 20, so it's 900% of 20. The correct answer is (E).