The number of shells in fred's collection is 80% of the number in phils collection. If Phil has 80 more shells than Fred, how many do they have altogether?

Answer: Fred and Phil have 720 shells altogether.

Step-by-step explanation:

To solve the question, create two equations using the information supplied in the question. Solve these equations to find the number of shells that they each have then add these together. Note than 80% percent is 0.80 in decimal form.

Let Phill's number of shells be x.

Let Fred's number of shells be y.

y = 0.80x ... equation 1

x = 0.80x+80 ... equation 2

Solving equation 2:

1x-0.80x = 80

0.20x = 80

x = 80/0.20 = 400 shells

Therefore y = 0.80*400 = 320 shells.

Total = 400+320 = 720 shells.