The average of 27 numbers is 20.The average of first 13

What value should come in place of question mark (?) in the following question. (You need not to calcualte the exact value)

(36.004 + 34.997)

Let {x + (1/x)} = 4, then Determine the value of {x² + (1/x²)}

 If x + 1/x = 5, then find [x² + (1/x²)].

If (a² + 1/a²) = 38, then find the value of (a³ - 1/a³).

Length of each side of a rhombus is 13 cm and one of the diagonal is 24 cm. What is the area (in cm²) of the rhombus?

(m - 4) ² + (n + 5) ² + (p - 3) ² = 0, then find the value of 2m + 3n - p.

If 112 ÷28 x 2² –12 x 6 ÷ 3 +12 = z, then find the value of z.

If x/y = 5/3, Find (x+y)/(x-y)?