A scientist estimated that a mixture would need 5 millimeters of a chemical to balance. The actual amount d was 7 millimeters. What was the percent error of the scientists estimation?

29%

Step-by-step explanation:

If 7 is 100% correct then 5 would only be a portion of it

So you need to divide 5 by 7

So 5 divided by 7 is .714 or .71

this means the error was 29%

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.