There seems to be something missing. Either a missing diagram or more context to the problem, or perhaps more instructions. I'm not exactly sure.
Anyways, if you simply need to solve the equation for x, then... 3x+7 = 5x-9 3x+7-3x = 5x-9-3x ... subtract 3x from both sides 7 = 2x-9 7+9 = 2x-9+9 ... add 9 to both sides 16 = 2x 2x = 16 2x/2 = 16/2 ... divide both sides by 2 x = 8
I'm assuming after this point, you'll use x somehow to determine the length of segment AD. Unfortunately there isn't enough info provided to do that, but I'll let you take over from here.
You have to find the difference in height between both checkpoints. To do this just calculate 196 - 52. Checkpoint 5 is 144 (meters?) higher than Checkpoint 2.
