Explanation:
you are in college, and need help with that ?
remember,
a > b
then also
a × c > b × c
c × a > c × b
and that is what we have here
a = 20, b = 30, c = 1/2
so, 30×1/2 is larger.
because 30 > 20.
a = 2/3, b = 2, c = 15
15×2 is, of course, larger.
because 2 > 2/3.