Sometimes it helps to draw it out...
(17)
C_______M_________Q
|___________________|
21
therefore, CM + MQ = CQ
17 + MQ = 21
MQ = 21 - 17
MQ = 4 <===
Start by getting all terms with x on one side and all terms without on the other.
6x+7=8x-15
subtract 6x from both sides
7=2x-15
add 15 to both sides
22=2x
divide both sides by 2
11=x
We can find out he answer to the question by using the information given.
Since we know that Death Valley is the lower of the two spots, we can assume that we can add the difference in elevation to Death Valley to get the elevation of Mt Whitney.
-86+4,504=4,418
Th elevation of Mt Whitney is 4,418 meters above ground.
Hope this helps!
This is tricky but I worked out the answer is A