7 1/5 – 3 3/5 = (7×5+1) – (3×5+3) = 36/5 – 18/5 = 18/5 = 3 3/5.
15 1/3 – 8 2/3 = (15×3+1) – (8×3+2) = 46/3 – 26/3 = 20/3 = 6 2/3.
7 3/10 – 5 9/10 = (7×10+3) – (5×10+9) = 73/10 – 59/10 = 14/10 = 7/5 = 1 2/5.
