Two trains on opposite tracks leave the same station at the same time. One train travels at an average speed of 80 km/hr and the other travels at an average speed of 70 km/hr. How long after they leave the station will they be 50 km apart?

Sally deposited money into a savings account paying 4% simple interest per year. the first year, she earned $75 in interest. how much interest will she earn during the following year? show your work and explain your reasoning in the space provided below.