I have some students who struggle with this, usualy it is because they need help visualising the question. I like to bring money into examples (they become more real).
Think of $100 as 100% of your savings. Your friend is asking you for 50% or half = so 100/50=2, that means you need to divide $100/2 to get 50%.
If your friend is less greedy and only wants 10%, same principle = 100/10=10; $100/10 =$10 dollars. I draw a little matrix when I do calcs with that same formula and try to visualise, what are they asking from me, what am I calculating etc.
If you can visualise the problem, it becomes less complex.
Hope this helps.