The absolute value of a number will never be negative because absolute value is the distance from zero, so it will always be positive. For example, you can't be -6 away from 0, you are 6 away from 0.
1/8 + 6/8 = 7/8
17 11/13 - 9 7/13 = 8 4/13
2/8 + 4/8 = 6/8 = 3/4
8/4 + 1/4 = 9/4 = 2 1/4
9/10 + 3/10 = 12/10 = 1 1/5
2 - 3/5 = 10/5 - 3/5 = 7/5 = 1 2/5
3/4 * 4 = 12/4 = 3
1/4 * 6 = 6/4 = 1 1/2
Train A weighs 181 tons and train B weighs 70 tons.