Answer:
X = 14
Let the unknown no. be X
mean= sum of all no. / no. of terms
17 = 15 + 17 + 20 + 22 + X+ X / 6
17 * 6 = 74 + 2X
102 - 74 = 2X
28 = 2X
28/2 = X
14= X
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