Answer:
$66
Explanation:
It can be convenient to assign a different variable to the amount of money each spent. We can call the amounts spent by Seedevi, Georgia, and Amy "s", "g", and "a", respectively.
The problem statement tells us ...
s = (1/2)g
s = a +6
s + g + a = 258
__
The problem statement asks for the amount Seedevi spent, so we need to find the value of s. It is convenient to write the other variables in terms of s:
g = 2s
a = s -6
Then the sum is ...
s + (2s) +(s -6) = 258
4s = 264 . . . . . . . . . . . add 6, simplify
s = 66 . . . . . . . . . . . . . .divide by 4
Seedevi spent $66.