a) 21 - ( 29 + x ) = - 12
= 21 - 29 - x = -12
= -8 - x = -12
-> -x = -12 + 8 = -4
=> x = -(-4) = 4.
b) 14 - ( x - 17 ) = - 31
= 14 - x + 17 = -31
= - x + 31 = -31
-> -x = -31 - 31= -62
=> x = -(-62) = 62.
c) 3 . ( x - 8 ) + 15 = 105
= 3x - 24 + 15 = 105
= 3x - 9 = 105
= 3x = 114
-> x = 38.
d) 2 . ( x + 4 ) - 16 = 98 + x
= 2x + 8 - 16 = 98 + x
= 2x - 8 = 98 + x
= 2x - x = 98 + 8
-> x = 106
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