1) 2 3/4 : 1 1/10 + 1 1/10 : 2 3/4 = 11/4 : 11/10 + 11/10 : 11/4 = 11/4 * 10/11 + 11/10 * 4/11 = 10/4 + 4/10 = 5/2 + 2/5 = (5*5 + 2*2)/(2*5) = 29/10 = 2 9/10
2) (4 5/18 * 6/7 - 2 4/9)^2 = (77/18 * 6/7 - 22/9)^2 = (33/9 - 22/9)^2 = (11/9)^2 = 121/81 = 1 40/81