Question 161833
12/(15+c)=9/(15-c)
9(15+c)=12(15-c)
135+9c=180-12c
9c+12c=180-135
21c=45
c=45/21
c=2.143 mph is the current.
Proof:
12/(15+2.143)=9/(15-2.143)
12/17.143=9/12.854
.7~.7