There are 150 shells. There are 10 more conch shells than starfish and twice as many sand dollars than conch shells. How many of each shell

Question

 How many of each shell are there?

Answer 1

s = number of starfish

s + 10 = number of conch shells

2(s + 10) = 2s + 20 = number of sand dollars

 

s + s + 10 + 2s + 20 = 150

4s + 30 = 150

4s =120

s = 30

 

30 + 10 = 40

2(30) + 20 = 60 + 20 = 80

 

There are 30 starfish, 40 conch, and 80 sand dollar shells.