The answer is
126
Square each value, add together, divide by numbers of values
(32 + 122 + 152) / 3 = (9 + 144 + 225) / 3 = (378) / 3 = 126
But the third clue seems to prohibit addition, so I'm not sure.
The third clue was changed to only prohibit subtraction.
Full list of equations:
(12 + 32) / 2 = 5
(12 + 42 + 52) / 3 = 14
(22 + 42 + 62 + 72 + 102) / 5 = 41
(72 + 132) / 2 = 109
(22 + 22 + 42) / 3 = 8
(12 + 42) / 2 = 8.5
(42 + 52) / 2 = 20.5
(22 + 42) / 2 = 10
(22 + 22) / 2 = 4