Please make sure it is correct it is important

Credit card a offers an introductory apr of 3.4% for the first three months and standard apr of 15.7% thereafter,

Atrain leaves little? rock, arkansas, and travels north at 90 kilometers per hour. another train leaves at the same time and travels south at 80 kilometers per hour. how long will it take before they are 680 kilometers? apart?

Asequence is a function whose is the set of natural numbers