Algebra
posted by Rayyan .
A quarium has a total of 28 beta fish, piranhas, and turtles. The number of piranhas is 1 more than the number of turtles, and 2 fewer than the number of beta fish. How many beta fish are there in the aquarium?

It's a system of equations problem. Just represent the values with different expressions as they relate.
givens:
28 animals total
number of piranhas = 1 more than turtles
number of piranhas = 2 less than number of beta fish
let x = number of piranhas
piranhas = x
turtles = x  1 (there's one less turtle)
number of beta fish = x + 2 (there are two more beta fish than piranhas)
now you can put all the expressions together and equate it to the total number of creatures in the tank.
x + x  1 + x + 2 = 28
simplifies to 3x + 1 = 28
now solve for x
3x + 1 = 28
1 1
3x = 27
/3 /3
x = 9
now plug this value in the expression you used to represent the beta fish 
(x + 2)
x = 9 so 9 + 2 = 11
there are 11 beta fish in the aquarium