Answer:
4/15 or 4:15
Explanation:
We know a ratio is basically for everyone of this we will have a "x" number of the other for example 
1:4 or 1:33 
In order to solve this, all our data should be in the same unit 
so in this case let's work with minutes 
48min : 3hr after converting 3hr to min we get...
48min : 180min
now we can simplify this to make this visually easier im going to use a fraction format 
 48 24 12 4
------- ÷2 ---------- ÷2 -------- ÷3 ----- I can not simplify any further
 180 90 45 15
So my answer is 4/15 or 4:15