Melody

It means how far is -5 from zero on  the number line.

What do you think that the answer is?

If two things are in the same proportion then they are enlargements or reductions of one another.

It can refer to numbers or shapes

Use asin

inverse sine and arc sine are the same thing :)

I did this is excel.  Is it what you want?

possible Wolfram|Alpha

2x+1=x

x=-1     this is NOT in the relevant domain so its no good

7-x=x

7=2x

x=3.5   not in given domain

10-2x=x

10=3x

x=10/3       YES

10-x=x

10=2x

x=5           YES

so there are 2 solutions

$$x=5\qquad or \qquad x=3\frac{1}{3}$$

 pleasse ask if you do not understand :)

Just multiply  both sides by  4/3

That is it!    

Hello Jeff

Chris has ALSO answered this here. 

I have answered on the original question.  :)