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If a + b = 12 and b = 5, then a = 7. Which Euclid axiom-type idea justifies replacing b by 5?

Class 9Euclid's PostulatesGeometry — Foundations
  • AThe whole is greater than the part
  • BEquals subtracted from equals give equals
  • CAll right angles are equal
  • DA line has length only

Step-by-Step Solution

From a + b = 12, subtract the equal quantities b and 5: a = 12 - 5 = 7. This uses 'if equals are subtracted from equals, the remainders are equal'.
Answer: B) Equals subtracted from equals give equals

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