dropped $3 means "-3", increased $6 means "+6"
the price dropped twice so 2(-3) and increased once by 6
so, 2(-3) + 6 = 0
the change in price is $0
18. -4, 4
19. -38, 38
20. -260, 260
21. -4092, 4092.
I might be wrong but...
No its not if this is a (X,Y). You cannot have 2 of the same x's and different Y's. You can have the same Y's with 2 different X's. Ask questions if you still need help :)
2/5=0.4
5/8=.625
subtract .4 from .625 and get....
.225
and .225 is 9/40