Question 906063
r*t=d
(51+c)*t=348
51*t+c*t=264
51*t-c*t=348
add
102t=612
t=612/102
t=6 hour
51*6+c*6=348
306+c*6=348
c*6=42
c=42/6
c=7 mph current
check
(51+c)*t=348
(51+7)*6=348
(58)*6=348
348=348

(51-c)*t=264
(51-7)*6=264
(44)*6=264
264=264
ok