The arithmetic sequence a; is defined by the formula:
ai= -3
ai = ai -1 – 5
Find the sum of the first 490 terms in the sequence.

Add the two expressions 3.8b - 7 and 2.9b + 9 enter your answer in simplified form

What is the interquartile range of this data set? 2, 5, 9, 11, 18, 30, 42, 48, 55, 73, 81

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?