Given: mean of 2, 7, 6 and x is 15

Mean =

⇒ _{15 =}

⇒ 60 = 15 + x

⇒ x = 60 – 15 = 45 …(i)

Also, given that mean of 18, 1, 6, x and y is 10

_{10 =} [∵ mean = 10]

⇒ 50 = 25 + 45 + y = 70 + y [from equation (i)]

⇒ y = 50 – 70 = - 20

Thus, y = - 20