Answer:
about 26 min
Explanation:
Toni rows a boat 4.5 km/h upstream and then turns around and rows 5.5 km/h back downstream to her starting point
First we find the average speed
We add both speed and divide it by 2

Now we find the distance for round trip
given total time is 48 mins. convert mins into hours
48 mins = 48 divide by 60 = 0.8
average speed = 5 km/hr
Distance = speed * time = 5 * 0.8 = 4 km
distance covered both ways = 4 km
so 4 divide by 2 = 2 km each way
To find time taken for upstream = distance of each way / speed of upstream
time =

Now convert hours into minutes
0.44* 60= 26.4 minutes