= = = =
①+-
② -(+)
③-(+)
④+++
⑤ ++-
⑥-(-)
① - +
②1+1.9+2.9+3.9+4.9+5.9
③ - + -
④ -( + )-
⑤5- +
⑥2.8×0.5+5×2.72