а) (2,3 + 5,8) * 3 5/7 / (4,9 - 2,3) * 5/9
= 8,1 * 26/7 / 2,6 * 5/9
= 8,1 * 26/7 * 9/2,6 * 5
= (8,1*26*9) / (7*2,6*5) = 190,62 / 91 = 2.09
б) 1/8 + (12,25 - 0,8) / (5/16 * (1 2/48 + 55/72) * 3 1/12 + 3 3/5)
= 0.125 + (11,45) / (5/16 * (50/48 + 55/72) * 37/12 + 18/5)
= 0.125 + 11.45 / (5/16 * (375/288 + 220/288) * 37/12 + 18/5)
= 0.125 + 11.45 / (5/16 * (595/288) * 37/12 + 18/5)
= 0.125 + 11.45 / (5/16 * (595/288) * 37/12 + 3.6) = 0.125 + 11.45 / (7.77 + 3.6) = 0.125 + 11.45 / 11.37 = 0.125 + 1.01 = 1.135
в) 0,21 * 1,25 / (13,6 - 11,1) = 0.2625 / 2.5 = 0.105
г) 2,781 / 2,06 + 7,825 / 3,13 = 1.35 + 2.5 = 3.85