36+29= 26-7= 32-6= 5+69= 7+67=
20+30+20= 50-20-10= 61-(47-7)=
29-29+51= 15+85-96= 65-(45-40)=
33+20-40= 78 +(82-80)= 78 + 2 - 60 =
图书角现在有多少本书?