8. Twelve less than something is: something - 12. Now, that something is twice a number. Let's call the number 'x', so that part is 2x:
[tex]2x-12[/tex]9. 5 more than a number is x+5, where x is the number. Then the quotient between that and -9 is that divided by -9:
[tex]\frac{x+5}{-9}[/tex]10. Four times something is that something multiplied by 4. That something is a number plus 0.7:
[tex]4(x+0.7)[/tex]