199. Найдите значение выражения:

1) (-5/14 + 9/15) : 17/30 = (-5*15 + 9*14)/(14*15) * 30/17 = (-75 + 126)/210 * 30/17 = 51/210 * 30/17 = (51*30)/(210*17) = (3*17*30)/(7*30*17) = 3/7.
2) (5/18 - 11/27) : (-2/16) = ((5*3 - 11*2)/54) : (-1/8) = (15-22)/54 * (-8) = -7/54 * (-8) = 56/54 = 28/27.
3) (11/18 - 17/24) : (5/18 + 4/15) = ((11*4 - 17*3)/72) : ((5*5 + 4*6)/90) = (44-51)/72 : (25+24)/90 = -7/72 : 49/90 = -7/72 * 90/49 = -(7*90)/(72*49) = -(1*10)/(8*7) = -10/56 = -5/28.