Just ask from another angle (unify the number of carrots)
Note: 2 radishes for 8 carrots (2×5= 10 radishes for 8×5=40 carrots).
And because: 10 radishes can be exchanged for five Chinese cabbages.
Five Chinese cabbages can be exchanged for 40 carrots.
40÷5=8 means 1 Chinese cabbage can be exchanged for 8 carrots (⊙ _ ⊙).
8×4=32 (roots) Four Chinese cabbages for 32 carrots.
-Mr. Da Dan is a guest O(∩_∩)O~