How do you solve 7x – 7 = 2x + 8?

2 Answers
Mar 30, 2016

x = 3

Explanation:

This is solved by simply moving the terms with x to the same side and the integers to the same side. You can do this by subtracting 2x from both sides and adding 7 to both sides. This gives:

5x = 15

Then divide both sides by 5, which gives x = 3.

Mar 30, 2016

x=3

Explanation:

The one rule you must follow is that what you do to one side of the equation you do to the other. Otherwise the 'equals' sign becomes false

Example: 7=7 this is true as the value on both sides is the same.

If I apply 7-2=7 this becomes false as we have 5=7 which is not true. How ever

7-2=7-2 is true. We have applied the action to both sides.
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This is why what I wrote is important:

Given:" "color(brown)(7x-7=2x+8)

Subtract color(blue)(2x) from both sides

" "color(brown)(7xcolor(blue)(-2x)-7=2xcolor(blue)(-2x)+8)

But 2x-2x =0

" "5x-7=0+8

Add color(blue)(7) to both sides

" "color(brown)(5x-7color(blue)(+7)=8color(blue)(+7)

But -7 +7 = 0

" "5x+0=15

Divide both sides by color(blue)(5)

" "color(brown)(5/(color(blue)(5)) x=15/(color(blue)(5)))

But 5/5=1" and "15/5= 3

" "color(magenta)(x=3)

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~