I'm French, I did the exercise but I don't know if it's right Use the comparative forms and at least three of the adjectives below :

easy / difficult / modern / old-fashioned / cheap / expensive / fast / time-saving /slow / varied

I don't understand sentence number 2.

How I read it is: "The choice on the net is less difficult than I'm stones because more varied"

I'm I, right?

On sentence number 4 I would remove the word "is" after the word "and" .

On sentence number 7 I would change the word "is" with the word "are" - because the word "articles" is plural

we need the passage first

substitute y = 2x - 4 to x + 2y = 12:

x + 2(2x - 4) = 12     use distributive property

x + (2)(2x) + () = 12

x + 4x - 8 = 12     add 8 to both sides

5x = 20     divide both sides by 5

x = 4

put the value of x to the first equation:

y = 2(4) - 4

y = 8 - 4

y = 4