To find the Volume of the Rectangular Prism, you'll need to multiply all of the measurements together. So you'll need to multiply 7, 9, and 11 together.
V=7*9*11
First, you'll need to multiply 7 and 9. Once you've multiplied 9 and 7 together, you should have 63. Now you should multiply 63 and 11 together. Once you've multiplied 63 and 11 together, you should have a Volume of 693
So if he already biked 25 miles we can subtract 80 and 25 which will get a total of 55. if we divided 55 miles to the rest of the 5 days he will have to bike 11 miles each day