Picture

The μὲν ... δὲ contrast again. Dikaiopolis μὲν does one thing, he ἐλαύνει τοὺς βοῦς ; the oxen δὲ do something else, they ἕλκουσιν (drag) the plough.
Several actors, different actions: while #1 does this, #2 does that, #3 does the other:
#1 μὲν... , #2 δὲ ..., #3 δὲ ...etc. Sounds good to me. Want another example? Here goes:
ὁ μὲν ἄνθρωπος proposes, ὁ δὲ θεὸς disposes.
τί βλέπομεν ἐν τῇ εἰκόνι; What do we see in the picture?
ἡ εἰκών gave us "icon".
Greek orthodox icons (
εἰκόνες) are just that, pictures (of saints e.g.).
  • Don't let these forms bother you, dative singular for instance always ends in ι
    iota subscript for 1st and 2nd declension words:
    ἐν τ ἀγρ, in the field (where? dative for position)
    παρέχω σῖτον τ Μαρί, I give food/bread to Mary.
    real iota for 3rd declension, like here:
    ἐν τῇ εἰκόνι, in the picture (where?)
τί βλέπομεν ἐν τῇ εἰκόνι ;
βλέπομεν   τὸν αὐτουργόν
τὸ ἄροτρον
τὸ κέντρον
τοὺς βοῦς
ἀλλὰ οὐ βλέπομεν τὸ δένδρον

 
By the way, that funny-looking tree in lessons 1b and 3b is a stylized olive-tree. The real tree is much fuller, has much denser foliage, but the leaf formation tells us that it is an  ἐλαία. It is because of this olive tree that Athena became patron goddess of Athens. How did that come about?
There are quite a few different versions told, but the story is basically the same. Here's one of them:
Once upon a time there was a small village called Kekropia ruled by an Egyptian king called Kekrops. He was a good man, so the gods Athena and Poseidon wanted to reward him. They had themselves a little contest, who will come up with the perfect present? Poseidon, the god of the seas gave him the horse (τὸν ἵππον). Useful for racing games, for war, also for pulling things. Well, they already had the ox. The goddess Athena's gift was the olive tree. And she won the contest, for without doubt the olive tree was the best present anybody could have imagined for Greece. It grows anywhere, doesn't need too much water (in short supply in those parts), and gives shade (the tree itself, with its thicker foliage), warmth (its wood), light (oil) and food (olives, oil). Small wonder the small village grew into a big polis named Athens (after its patron-goddess).
And the Parthenon (from ἡ παρθένος the young girl, maiden, virgin) was built in honour of the young goddess, up on the Acropolis, overlooking her town.