B: 160*2/5-6=58 tons.
1 * * * delivery: 84+58= 142 tons.
Sorry, I read the wrong question just now.
More than two-fifths of the 20 tons were transported by the A-pile, which means that the A-pile transported 2/5 instead of 2/5 of the total number of the two piles; Two-fifths of the B piles are less than six tons, which means 2/5 of the B piles, not 2/5 of the total number of the two piles.
Solution: estABlish a rectangular coordinate system with the center o of the semicircle as the coordinate origin and the straight line ab as the x axis, a