Answer:
3
Step-by-step explanation:
Remember that when we are dividing two exponents with the same base (here, it's 13), we can subtract the values of the powers:

So, here, we have
, so we subtract 7 from 10:

Thus, 3 should go in the box.
The second one: 4 times 10 to the power of 12
Hello!
If y varies jointly with x and z, it'll mean that x and z are being multiplied by a factor "k", to equal y.
To give you a visual, this is what I mean.

That means we'll want to find
with the first point we're given: 



Which means our equation is:

Now, let's plug in the
and
from the other point to find
.


Hope this helps!
Volume=width*length*height
So the volume is
V=8*6*13=624cm^3
I hope this helped :)