Enigma 1457 — Anglo-Italian sums

by Richard England

Within each of these Anglo-Italian sums, digits have been consistently replaced by capital letters, different letters being used for different digits. However, the three sums are entirely distinct — a letter need not have the same value in one as in either of the others. No number starts with a zero.     
    (a) FOUR + FOUR = OTTO
    (b) TWO + TRE + FIVE = DIECI
    (c) THREE + NOVE = DODICI

What are the numbers represented by
OTTO in (a), DIECI in (b), DODICI in (c)?