2kg + 40ons- 2,000gram

1 kg = 1.000 gram 》 2 kg = 2.000 gram
1 ons = 100 gram 》 40 ons = 4.000 gram

jadi 2kg + 40ons- 2,000gram =
2.000 gram + 4.000 gram – 2.000 gram
= 2.000 gram
= 20 ons
= 2 kg