If a + b = 20 and a - b = 6, then what is a × b?

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Accepted Answer

1. Add the equations: $(a+b)+(a-b)=20+6$ so $2a=26$ and $a=13$.
2. Substitute: $b=20-a$, so $b=7$.
3. Multiply: $a	imes b=13	imes7=91$.
FINAL_ANSWER: d

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