given that 1 ox eats as much as 10 sheep:
4 oxen = 40 sheep
therefore,
first farmer: the equivalent of 40 sheep
second farmer: 30 sheep
that means 30+40 = 70 animals eating
$140 ÷ 70 = $2
so it is $2 per eat
2 x 40 = $80 for the first farmer's oxen
2 x 30 = $60 for the second farmer's sheep