Given:
The cost of a smaller arrangement by Sparrowtown Florist, s=$13.
The cost of a large centerpiece by Sparrowtown Florist, S=$29.
The cost of a smaller arrangement by Michelle's Flowers, m=$12
The cost of a large centerpiece by Michelle's Flowers, M=$51.
Let x be the number of smaller arrangements ordered by Vega from Sparrowtown Florist and y be the number of smaller arrangements ordered by Vega from Michelle's Flowers.
Given, the cost of smaller arrangements ordered by Vega will be the same at either flower shop.
The cost of smaller arrangement ordered from Sparrowtown Florist is,

The cost of smaller arrangement ordered from Michelle's Flowers is,

Hence,

Using the above ratio , we can write, x=13n and y=12n where n is a constant. Let n=1.
If we put x=12 and y=13 in equation (1),

Hence, the number of smaller arrangements is,

Now, the total cost of smaller arrangements per shop is,

Hence, if Vega orders 25 smaller arrangements, it will cost $156 at either shop