The Rivera family spend ( 9% + 3% = 12% ) of their income ( $4800 ) on transport, we need to know how mucvh this is...

Therefore it's clear the Rivera family spend $ 576 monthly and the Wagner spend $ 560 on transportation. Turning the wagner's money into percentage, we do...

The wagner spend 14%.
The wagner family pays $ 560 which is 14% of their $4000 income. The other family pays a total of 12%. Hence the Wagner family pays a larger part of their income on transportation.