u = number of rows at first

Before 16 chairs,  number of chairs = 11 u

After 16 chairs, number of chairs = 8 (u+14) = 8u +112

11u + 16 = 8u + 112

3u = 96 => u= 32

Hence total chairs in concert hall = 11(32) +16  or 8 (32+14) = 368