Question 1073934
Let n be the initial speed of the ship. Then the increased speed would be n+5. So:
48/n + 78/n+5=12
48(n+5)+78n=12(nē+5n)
126n+240=12nē+60n
12nē-66n-240=0
2nē-11n-40=0
(2n+5)(n-8)=0
n=-5/2 or 8
Throwing out the negative value, we get the initial rate of the ship to be 8 mph. ☺☺☺☺