Question

Tính hợp lí: 

8 - 10 + 12 - 14 + 16 - 18 + 20

Answer 1

   8 - 10 + 12 - 14 + 16 - 18 + 20

= 8 + (12 - 10) + (16 - 14) + (20 - 18)

= 8 + 2 + 2 + 2

=14

Answer 2

  8-10+12-14+16-18+20

=8+(12-10)+(16-14)+(20-18)

=8+2+2+2

=14