`A = 3/(4 xx 7) + 3/(7 xx 10) + ... + 3/(91 xx 94)`

`A = 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/91 - 1/94`

`A = 1/4 - 1/94`

`A = 45/188`

`***` $\color{#DCDCDC}{O}$$\color{#BEBEBE}{b}$$\color{#F5F5F5}{a}$$\color{#D3D3D3}{n}$$\color{#F8F8FF}{a}$$\color{#FFFFFF}{i}$