1)
(7,8 * 2,7) / (9 * 0,3 * 3,9) = (6 * 0,9) / (3 * 0,3 * 3) = 6/3 = 2,
2)
(8а + 16а) / (2* 8а) = 24а / 16а = 3/2 = 1 1/2 (или 1,5),
3)
(31*90 - 35*31) / (5*31) = 31*(90-35) / (5*31) = (31*55) / (5*31) = 55/5 = 11,
4)
(57х + 19х) / 19х*4 = 76х / 76х = 1