11 + 3 × 7 × 9 ÷ 10 × 80 ÷ 7/5 - 2/3 + 7/9
= 11 + 21 × 9 ÷ 10 × 80 ÷ 7/5 - 2/3 + 7/9
= 11 + 189 ÷ 10 × 80 ÷ 7/5 - 2/3 + 7/9
= 11 + 189/10 × 80 ÷ 7/5 - 2/3 + 7/9
= 11 + 1512 ÷ 7/5 - 2/3 + 7/9
= 11 + 1080 - 2/3 + 7/9
= 1091 - 13/9
= 9806/9
bài gì deso
hic