Question

Translate the sentence into an equation or an inequality. -9 is equal to a number \(y\) decreased by \(21 .\)

Short answer

\(y - 21 = -9\)

Step-by-step solution

Analysis of Sentence

The first part of the sentence has '-9' which is the result. The last part of the sentence has 'a number y decreased by 21'. 'Decreased by' implies subtraction in the mathematical operations. We need to form a equation using these items.

Formulate Equation from Sentence

The sentence is translated as: the result of subtracting 21 from a certain number y is equal to -9. In mathematical terms, this can be expressed as \(y - 21 = -9\). The minus sign in front of the 9 is because of 'decreased by', which indicates subtraction.

Check the Equation

Check the equation to ensure that it matches the original sentence. The left part of the equation should mirror 'a number y decreased by 21' and the right part should correspond to '-9'. Verify whether \(y - 21 = -9\) accurately reflects '-9 is equal to a number y decreased by 21'