Translation:They turn on computers and learn English.
"Máy" means machine and "Tính" means to calculate. So litterally it means a machine that can calculate. The computer is a machine that can calculate like the calculator with more capability, so this term is use for both. In vietnamese conversation, "máy tính" is use as a slang term for computer. That is my understanding.
I could be wrong, but my sense of it is that in Vietnamese "bất máy tính" means the act of turning a computer on in general. So they do it, and learn English. Similar to saying "they breathe air, and start running", or "they eat rice and feel full". In English we feel the need to specify if it is one or more computers, but in Vietnamese it is more like with uncountable things in English. We don't need to specify how much air or rice is eaten, we just understand that the action of breathing air happened, that the action of eating rice happened, and that is enough for us. The same for Vietnamese in this sentence. We know those people performed the act of turning on one or more computers, and that is enough.