a) 5555-(55÷5+a+5555÷5+555÷5)÷5=5255
5555-(11+a+1111+111)÷5=5255
(11+a+1111+111)÷5=5555-5255
(11+a+1111+111)÷5=300/×5
a+1233=1500/-1233
a=267
b) 2009-(126×7×0+288÷9+a)=1
0+32+a=2009-1
32+a=2008/-32
a=1976
c) 4×(2000÷100+1968÷8-a)=0/÷4
20+246-a=0
266-a=0
a=266-0=266