1. a) 4×10÷5×4-18÷2×3+68=
4×2×4-9×3+68=
32-27+68=
5+68= 73
b) 72-10÷2×5+21÷7×8=
72-5×5+3×8=
72-25+24=
47+24=71
c) 91-(64÷8×5÷10)×6+81÷(13-4)=
91-(8×5÷10)×6+81÷9=
91-(40÷10)×6+9=
91-4×6+9=
91-24+9=
67+9=78
2. a=9×3=27
b=56÷7=8
c=0÷10=0
a-(b+c)= 27-(8+0)=27-8=19
(a×c)÷b=(27×0)÷8=0÷8=0
(b×c)+a=(8×0)+27=0+27=27
3. (3×9)-8÷2+16÷4=a
27-4+4=a
23+4=a
27=a -> a=27
Sper că te-am ajutat :3