`\color{#c90000}{♡}\color{#c94e00}{N}\color{#c9aa00}{g}\color{#85c900}{u}\color{#42c900}{y}\color{#00c901}{ễ}\color{#00c94b}{n}\color{#00c996}{~}\color{#00b9c9}{M}\color{#006ec9}{a}\color{#0024c9}{i}\color{#2700c9}{~}\color{#6200c9}{T}\color{#9c00c9}{r}\color{#c900c4}{à}\color{#c9008a}{~}\color{#c90048}{M}\color{#c90000}{y}`

`A = 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56`

`A = (1 - 1/2) + (1 - 1/6) + (1 - 1/12) + (1 - 1/20) + (1 - 1/30) + (1 - 1/42) + (1 - 1/56)`

`A = (1 + 1 + 1 + 1 + 1 + 1 + 1) - (1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56)`

`A = 7 - (1/(1.2) + 1/(2.3) + 1/(3.4) + 1/(4.5) + 1/(5.6) + 1/(6.7) + 1/(7.8))`

`A = 7 - (1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8)`

`A = 7 - (1 - 1/8)`

`A = 7 - 7/8`

`A = 49/8`

Vậy `A = 49/8.`