Your Nine is Four

In Indonesia, to value student's exam is not A, B, C, and so on, but from 1 to 10.. So, here's one of jokes tells about it

A father who have 2 son (Útú and Aló) is leaving for his duty in other town.
Father: "Útú, Aló, I'm leaving now. Útú, I want you to watch your brother, I heard he's got detention because he's too lazy to go to school.
Útú: "Yes father."
Father: "Aló, you study hard alright.. if your "9" is four, I'll bring you motorcycle..!!
Aló: "Alright..!! that's cool dad.!!"
Then the father leave for two months for his duty. Soon after two months, the father call Útú to ask the younger brother's condition..
Father: "Hallo Útú, how's your brother?"
Útú: "Well he's fine dad, he's about to show me his examination results."
Then Aló came and flashes his examination results to Útú..
Útú: "Dad.. it's a little bit blur but l think l see four "9" in the result.."
Father: "Motorcycle is on the way..!!"
Soon the father arrive home with truck loaded with motorcycle..
Father: "Where is the result Útú?"
Útú: "I think he put it on the shelve."
The father took the result book and search the four "9"..
Father: "He's got "9" in art.. Great..!! But what is this? 9 days sick, 9 days without news, 9 days skipping classes..!!? So he does got four "9"... Útú.!! where is your brother..!!
Truck driver: "Sir, I think your son took the motorcycle and leave."
Father: "@#%+"