A= 3.4.5 + 4.5.6 + 5.6.7 +....+ 22.23.24

`A=3.4.5+4.5.6+...+ 22.23.24`

`4A = 3.4 .5 .4 + 4.5 .6 .4 + ...+ 22.23 .24 .4`

`4A = 3.4 .5 . ( 6 -2 ) + 4.5 .6 . ( 7-3 ) + ... . . + 22.23 .24 . ( 25-21 )`

`4A = 3.4 .5 .6-2.3 .4 .5 + 4.5 .6 .7-3.4 .5 .6 + ... . + 22.23 .24 .25- 21.22 .23 .24`

`4A= 22.23 .24 .25`

`A=(22.23.24.25)/4`

`A=303600/4=75900`