Преобразуйте десятичные дроби в обыкновенные и вычислите.

1) 0.2 + 1/7 = 2/10 + 1/7 = 14/70 + 10/70 = 24/70 = 12/35. 2) 7/16 - 0.12 = 7/16 - 12/100 = 175/400 - 48/400 = 127/400. 3) 4.85 - 2 13/24 = 485/100 - (48/24 + 13/24) = 485/100 - 61/24 = 1164/240 - 610/240 = 554/240 = 277/120. 4) 7 8/21 - 4.375 = (7 + 8/21) - 4.375 = (147/21 + 8/21) - 4375/1000 = (155/21) - (875/200) = 3100/420 - 18375/420 = -15275/420 = -3055/84.