4 Answers

3 x 7 = 21
9 x 8 = 72
if the pattern is to multiply successive integers (7,8,9…) by powers of 3, then the next multiplier would be 3 to the 3rd power, so:
27 x 9 = 243

Seems like it alternates.
The odd slots are filled with 7, 8, 9.
The even slots are filled with (previous slot * 3), (previous slot * 3^2).
So the next slot, which is even, should be (previous slot * 3^3), or (9 * 27), which is 243.

first term = 7
second term = 7.3 = 21
third term = 8
fourth term = 8.3^2 = 8.9 = 72
fifth term = 9
sixth term = 9.3^3 = 9.27 = 243
seventh term = 10 and next term may be 10.3^4 etc

No