Answer: bd=8 dc=2 and ae=4 so value of ab=16
Step-by-step explanation:
This is a geometric progression problem. We can the general formula that can tell us how many flowers would be planted each month.
Let's write the terms that we know and see if we can find the pattern:

The patern here is obvious. Let's write it down:

This formula gives us a number of flowers planted in the n-th month.
You would multiply 9x___ whatever the other number is witch is 4
I think this is more of an opinion question. What someone could solve mentally may not be the same as someone else's.If it were my worksheet, I'd circle all of them but it may be different for you.
At your level, I'd probably circle:
54 - 10
93 - 20
and 39 - 2