Line ab is parallel to line cd what is the measure of 4

Imagine a new pasture with grass growing on it. every day after the seeds have germinated, the number of blades of grass in the pasture triples. after 18 days, the entire pasture is completely covered in grass. how many days did it take for the pasture to be one-third covered in grass?

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Use a standard normal table to determine the probability. give your answer as a decimal to four decimal places. −1.5< < 1.5)