I am not sure of my workings but here it is:

$\displaystyle 20-3y = y+4$

$\displaystyle 20-4 = y+3y$

$\displaystyle 16=4y$

$\displaystyle y=4$

Therefore, $\displaystyle y>4$

Also, how do I illustrate the answer on a number line? Not quite sure what they are asking for