Velocity of swimmer in still water = Velocity along width of river = 1.20 m/s
So, time taken by the swimmer to cross the river = 150/1.20 = 125 seconds
So , the swimmer is going downstream for 125 seconds at a speed of 0.55 m/s
Distance traveled during that time = 0.55*125 = 68.75 m
So the swimmer will reach 68.75 m far from the point opposite to her starting point