209 - ( ( 145 + х ) - 12 ) + 96 = 123

209 -((145 +х) - 12) + 96 = 123209 - (145 +х -12) + 96 = 123209 - 145 - х + 12 + 96 = 123-х = 123 - 209 + 145 - 12 - 96-х = - 49х = 49