Question 753825
The assumption that neither of those trips makes necessarily a round-trip.


Let c = stream current speed
let r = the boat speed in no current of steam


Combination___________rate___________time____________distance
4hd,3hu_______________{{{(r+c)}}},{{{(r-c)}}}___4,3__________{{{highlight((r+c)4+(r-c)3=116)}}}
3hd,4hu_____________{{{(r+c)}}},{{{(r-c)}}}____3,4___________{{{highlight((r+c)3+(r-c)4=108)}}}


The equations making up the system are shown under "distance" column.  We are not given any of the rates; only we have times and distances.  We can solve the system for both rate variables.


Simplifying the distance equations-----
{{{(r+c)4+(r-c)3=116}}}
{{{4r+4c+3r-3c=116}}}
{{{highlight(7r+c=116)}}}
AND
{{{(r+c)3+(r-c)4=108}}}
{{{3r+3c+4r-4c=108}}}
{{{highlight(7r-c=108)}}}


The simpler system is really
{{{highlight(7r+c=116)}}}
{{{highlight(7r-c=108)}}}