18 * (1/9)^2 - 20 * 1/9
18 * 1/81 = 18/81 - 20/9 = 18 - 180/81 = -162/81 = -2
4/25 + 15/4 = 1+ 375/100 = 391/100 = 3,91
(19/8 + 11/12) / 5/48
19/8 + 11/12 = 228 + 88/96 = 316/96
316/96* 48/5 = 316/10 = 31,6
12/20 * 3 = 12/60 = 6/30 = 2/10 = 1/5
1/4 + 0,7 = 1/4 + 7/10 = 5 + 14/20 = 19/20