a) 0,(2) + 0,(6) = 0,222...+0,666... =
= 0,888... = 0,(8)
b) 0,(13) - 0,(4) =
= 0,131313... - 0,44444... = - 0,(31)
0,4444... -
0, 1313
-------------
0,3131..
c) 1,(7) + 0,(6) = 1,777...+0,666... =
= 2,443... = 2,(4)
d) 3,(17)+0,(48) - 2,(39) = 3,171717...+0,4848 -2,(39) =
= 3,656565... -2,(39) = 3,(65) -2,(39) =
= 3,656565... - 2,393939... =
= 1,262626... = 1,(26)