b + f = 8
where b is the current bus fare and f the current ferry fare.
1.10b + 1.25f= 9.25. Replace f with 8- b:
1.10b + 1.25(8-b) = 9.25
Then:
1.10b-1.25b + 10 = 9.25, and so
-0.15b = -0.75. Then b = -0.75 / (-0.15) = 5
The bus fare is current $5, and so the ferry fare is $3.