Answer: We need to support her work for at least 15 days.
Explanation:
Juana's mother receives a daily payment of 30 soles .
She has already 120 soles.
Let x = Number of days to save at least 550 soles.
Then, Total she has after x days = 120+30x
According to the question, we have

i.e. minimum value for x=15
Hence, we need to support her work for at least 15 days.