Bỏ dấu ngoặc rồi tính các tổng sau

a) 1711−65−1611+265

=1711−65+1611+265

=1711+1611+265−65

=1711+1611+265−65

=3311+205

=3+4

=7

b) 395+94−95−54+67

=395+94−95−54−67

=395−95+94−54−67

=395−95+94−54−67

=305+44−67

=6+1−67

=7−67

=497−67

=437