Since, a number can be written as the sum of the place value of all of its digit.
That is, we can write,
AAA=100A+10A+A
And, 299A=2000+900+90+A.
Here, the given expression,
2222+99+9+AAA=299A
⇒2222+99+9+100A+10A+A=2000+900+90+A
⇒2330+111A=2990+A
⇒111A−A=2990−2230
⇒110A=660
⇒A=6
Hence, the value of A is 6.