Answer:
5/1 (below for more possible answers)
Explanation:
Proportional is a corresponding in size,
15/3 is equal to 5 (5/1) 15 divided by 3
also possible answers...
10/2
20/4
25/5
30/6
35/7
40/8
45/9
50/5
55/11
60/12
65/13
70/14
75/15
which all these equal 5