I'll help you out a little bit
first of all, distribute the number next to the parenthesis to the numbers inside
so...
4a + 20 ≥ 5a + 15
then you will subtract the 15 from one side to another
4a + 5 ≥ 5a
then subtract 4a from the left side to the right
5 ≥ a
There you have it!
Hope this helps :)