Tính nhẩm:

$\eqalign{ & 14 - 9 = ..... \cr  & 16 - 7 = ..... \cr  & 12 - 8 = ..... \cr  & 6 + 9 = ..... \cr}$     $\eqalign{& 8 + 8 = ..... \cr & 11 - 5 = ..... \cr & 13 - 6 = ..... \cr & 18 - 9 = ..... \cr}$

$\eqalign{ & 14 - 6 = ..... \cr  & 17 - 8 = ..... \cr  & 12 - 5 = ..... \cr  & 3 + 9 = ..... \cr}$      $\eqalign{& 9 + 4 = ..... \cr & 11 - 9 = ..... \cr & 3 + 8 = ..... \cr & 16 - 8 = ..... \cr}$