Efetue: :
a)-1-2-3=
b) -4-5-8+ 10 =
c)-7 + 20 - 15 + 20 -1 =
d) -13 + 7 - 9 +5 -13 =
e)-20 + 10 - 10 + 20 + 14 - 13 - 1 =
f)-8- 10+ 17-3+4 7+8-1=​