allie need to buy at least 12 candles plain candles sell for 4 each and scented candles sell for 7 each she can spend no more than 57

there were 9 plain candles and 3 scented candles.

Explanation:

Let she buys x candles for 4 each and buys y candles for 7 each.

Then According to the questions

x+y = 12 ... 1

and

4x+7y = 57 ... 2

solving 1 and 2 we get the values of x and y as 9 and 3 respectively.

So, there were 9 plain candles and 3 scented candles.