Answer:
Serena had $32 at the end.
Explanation:
They both had x in the beginning.
Bryan donated $258, so now he has
x - 258
Serena donated $234, so now she has
x - 234
Serena now has 4 times as much money as Bryan.
x - 234 = 4(x - 258)
x - 234 = 4x - 1032
-3x = -798
x = 266
They both had $266.
$266 - $234 = $32
Answer: Serena had $32 at the end.