Answer 1

13x - 5 < 15x + 4 < 7x + 12, x ε R

Take 13x - 5 < 15x + 4 

13x < 15x + 9

0 < 2x + 9

-9 < 2x

`-9/2 < x`

and

15x + 4 < 7x  + 12

15x < 7x + 8

8x < 8

x < 1

`:. -9/2 < x < 1`

i.e -4.5 < x < 1

∴ Solution set = {x : -4.5  < x < 1, x ∈ R}

The solution on the number line is as follows: