Answer:
Therefore, we conclute that the map distance between A and C is 35 m.u..
Step-by-step explanation:
We know that the order of three loci is A B C, and the map distance between A and B is 15 m.u., and the map distance between B and C is 20 m.u. We calculate the map distance between A and C.
Therefore, we get

Therefore, we conclute that the map distance between A and C is 35 m.u..
We can distribute
2(5)+2(-x)=10-2x
we get
8+10-2x=?
18-2x=?
whatever that ? is, we don't know
multiply both sides by -1
2x-18=-?
add 18 to both sides
2x=18-?
divide bth sides by 2
x=9-(?/2)
whatever the left side it, just divide it by 2 and subtract it from 9