When using a modal verb (können, dürfen, mögen, sollen, müssen, wollen), the modal verb is conjugated and goes in the second position. The second verb is not conjugated and gets thrown to the very end.
It's not really applicable to this simple sentence, but anything else that goes in between typically follows the word order of TIME, MANNER, PLACE. For instance:
Ich muss um drei Uhr mit meiner Schwester nach Wien fahren. (I must drive with my sister to Vienna at 3:00.)
TIME: um drei Uhr
MANNER: mit meiner Schwester
PLACE: nach Wien
yes i don't get why he is not able to read doesn't work there, any luck? any suggestions?
I guess it's more or less the same thing. Although Duolingo focuses more on the literal meaning, so I guess we got to live with it. "Kann" technically speaking however is equivalent to Can, so perhaps that's why.