0,9*(1 5/9-4/9:(5/8+3/8:3))*

= 13/15

0,9 * (1 5/9 - 4/9 : (5/8 + 3/8 : 3)) = 9/10 * (14/9 - 4/9 : (5/8 + 3/8 : 3/1) = 9/10 * (14/9 - 4/9 : (5/8 + 3/8 * 1/3) = 9/10 * (14/9 - 4/9 : (5/8 + 1/8)) = 9/10 * (14/9 - 4/9 : 6/8) = 9/10 * (14/9 - 4/9 * 8/6) = 9/10 * (14/9 - 32/54) = 9/10 * ((84-32)/54) = 9/10 * 52/54 = 52/60 = 26/30