Please help me asap! Thanks in advanced guys! :)

I think I did it wrong but I try

Step-by-step explanation:

8x+20+11x-31

-8x       -8x

20-31 =3x

+31   +31

51  =3x

17=x

ik how do do this just give me a few minutes and i will give it to

  or  

step-by-step explanation:

if the four friends split the cost, p, of the pizza evenly, then each friend pays one-fourth of the cost of the pizza.

the expression is   or