Answer:

1981

Step-by-step explanation:

Let 1997 + x be the required answer.

The mother is six times old as the son, we can write it as:

46 + x = 6(21 + x)

=> 46 + x = 126 + 6x

=> 6x - x = 46 - 126

=> 5x = -80

=> x = -16

Therefore, the required answer is 1997 + (-16) = 1981.