Theory

➡ Average = Sum of all the Values / Total Number of Values

The average (arithmetic mean) of a and b is 10

Average = \(\frac{Sum}{2}\) = \(\frac{a + b }{2}\) = 10 (given)
=> a + b = 10*2 = 20 ...(1)

The average of c and d is 7

Average = \(\frac{Sum}{2}\) = \(\frac{c + d }{2}\) = 7 (given)
=> c + d = 7*2 = 14 ....(2)

Adding (1) and (2) we get
a + b + c + d = 20 + 14 = 34 ...(3)

The average of a, b, and c is 8

Average = \(\frac{Sum}{3}\) = \(\frac{a + b + c }{3}\) = 8 (given)
=> a + b + c = 8*3 = 24 ....(4)

(3) - (4) we get
a + b + c + d - (a + b + c) = 34-24 = 10
=> d = 10

So, Answer will be 10.
Hope it helps!

Watch the following video to Learn the Basics of Statistics

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