Answer:
138 : 269
Explanation:
Last year, the number of bicyclists that showed up was 1345.
This year, there were 690 bicyclists.
The ratio of the number of bicyclists that showed up for the past two years is the ratio of those that showed up this year to those that showed up last year:
690 : 1345
Let us put it in simplest terms:
138 : 269