The equation that represent how much Anne had initially to spend is x - 21 = 9 and the money she had initially is 30 dollars.
She bought a necklace for each of her three sisters. She paid $7 for each of the necklace. she had 9 dollars left after the expenditure.
Therefore,
let the money she had initially = x
Hence,
x - 7(3) = 9
x - 21 = 9
x = 21 + 9
x = 30
Therefore, the money she had initially to spend on each sister was 30 dollars.
learn more on equation here: https://brainly.com/question/900047
#SPJ2