how do I write in inequality form : all real numbers at most 6 units from 0 ?

|x-6| < 0

Solve: 7-4|x+7|>-5

7-4|x+7|>-5
-4|x+7| > -5-7
|x+7| < -12/(-4)
-3 < x+7 < 3
-10 < x < -4

A number n is no more than 7 units way from 5. Write an absolute-value inequality to show the range of possible values for n.

so that

|2r - 1| = 1/4. The answer was 3/8 and 5/8. We could figure out the 5/8 but how do you get 3/8?

it means:
2r-1=1/4
or
2r-1=-1/4 which leads to
2r=-1/4+1
2r=3/4
r=3/8

Find an equation of the line through the given points. Write the equation in standard form. Through (-1,1) and (1, -13).

m=(-13-1)/(1-(-1))=-14/2=-7
y-1=-7(x-(-1))
y-1=-7x-7
7x+y=-6

Martha is 1 year older than twice his sisters age. The difference of their ages is 8. Find their present ages.

1) M=2S+1
2) M-S=8
setting the equations up to solve...
M-2S=1
-M+S=-8

-S=-7
S=7
M=2(7)+1=15 

Simplify (21x^5w^3)/(9x^2w^10)