Answer:
462 
Step-by-step explanation:
Rectangular Prism: 7 x 8 x 6 = 336
Triangular Prism: (0.5 x 7 x 6) x 6 = 126
336 + 126 = 462
Answer:

Step-by-step explanation:
see the attached figure to better understand the problem
step 1
In the right triangle ABC find the length side BC
we know that


step 2
In the right triangle ABD find the length side BD
we know that


step 3
we know that
The distance between the two boats is the length side CD

substitute the values

20 with a number minus what will equal 9. ^_^