a21-a7=84 a21 = a+10d _ (1) a7 =a+6d _ (2) (1) - (2) = 84 a + 10d - a - 6d = 84 By above equation we obtained 4d = 84 Then d = 21 21 is correct answer

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Harshita Vatyani 7 years, 9 months ago

A21-A7=84 A+20d-(A+6d)=84 14d=84 d=6

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Rishabh Jain 7 years, 9 months ago

What is the. Question I cannot understand so plz told clearly

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Harshita Vatyani 7 years, 9 months ago

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