Two fishing boats depart a harbor at the same time one trave

Two fishing boats depart a harbor at the same time, one traveling east, the other south. The eastbound boat travels at a speed 2 mi/h faster than the southbound boat. After 3 h the boats are 30 mi apart. Find the speed of the southbound boat.
mi/h

Solution

Let the speed of southbound boat be x m/h

Therefore speed of eastbound boat=x+2 mi/h

After 3 hours,distance covered by southbound boat= 3x mi

And distance covered by eastbound boat=3(x+2) mi=3x+6 mi

Therefore we get

(3x)² + (3x+6)²= 30²

9x²+ 9x²+36+36x-900=0

18x²+36x-864=0

x²+2x-48=0

(x+8)(x-6)=0

x=-8,6

x=6mi/h