This is simple simplifying. If you need an explanation dm me.
here is the answer
x=-5
The slope is 5/2. You can find the slope by using y2-y1/x2-x1. 7-2/6-4= 5/2.
C=8h+12
the 8h represents the $8 per hour for renting the boat, and h represents however many hours you rent the boat for. The +12 is the initial $12 fee. This is in slope intercept form, just using different variables than y=mx+b
Answer:
-31/8. That's the answer to your question
Find the median first.
78, 80, 83, 85, 86, 87, 90. The middle one is 85, so there's the median. Take the upper half of this set, not including the median, 85, and then subtract 86 from 90. This is 4, so this is the interquartile range.
