So, to solve this problem you just need to combine the variables, and the constants (integers).
The first thing you should do is combine 18 and -11, which equals 7. So, instead of writing 18-11, you can write 7.
Your equation now is 7-4y+20
Now you can combine 7 and 20, which is 27.
Your final answer is 27-4y or -4y+27.