Merkitse puuttuvat luvut.

a. (14 + ) – (21 – 6)
= 43 –
=

b. 26 + 19 +
= 60 + 19
=

c. – 56 – 37
= 89 – 37
=

d. (656 – ) + ( – 423)
= 381 + 231
=