Britt has 4 full boxes plus 12 extra cds, and jim has 3 full boxes and 5 extra cds. if the number of cds in each box is represented by c, write an expression that shows the total number of cds that britt and jim have.

This is actually quite easy.  

Britt=4c+12 because 4 boxes and 12 extra

Jim=3c+5 because 3 boxes and 5 extra

option 3 . (5x + 1) - (-10x + 6)

step-by-step explanation:

option 1 :

(4x + 3) + (-9x + 4)

or 4x+3 -9x + 4

or -5x + 7

option 2

(x - 2) - (6x - 9)

or x-2-6x + 9

or -5x + 7

option 3

(5x+ + 6)

or 5x + 1 + 10x -6

or 15x -5

option 4

-4x+2x+7-3x

-7x + 2x + 7

-5x + 7

hence only option 3 did   not satisfy the given simplify expression.