А)
1 5/11 × (7 - 2 4/11) = 16/11 × (7 - 26/11) = 16/11 × (77/11 - 26/11) = 16/11 × 51/11 = 816/121 = 6ц. 90/121;
Б)
(4,2 : 1,2 - 1,05) × 1,6 = (42/10 : 12/10 - 1,05)×1,6 = (42/10×10/12 - 105/100)×1,6 = (21/6 - 105/100)×1,6 = (1050/300 - 315/300) × 16/10 = 735/300 × 16/10 = 3,92