Most of the question is pointless mathematics to confuse you, and has very little to do with how you would calculate mass and balance. Nevertheless, the answer is as follows...
If they told you the mass of the aircraft it would be far too easy, so instead they tell you that it has 6 wheels, four big ones and two little ones. The big ones each carry 6000 kg and the little ones each carry 725kg, and they would like you to add them up.
Using your trusty calculator you will find that the four big ones therefore carry 24000 kg between them, whilst the two little ones carry 1450 kg, for a total mass of 25450 kg between all six wheels.
At which point it is fairly simple to observe that the little wheels are carrying 5.7% of the total mass, so the C of G must be 5.7% of the distance between the big and little wheels. You're told that the total distance is 10 metres, so we'll accept 57cm as the answer, and move on to the next one
