Question

In seans fish tank, there are 6 times as many goldfish as guppies. There are a total of 21 fish in the tank. How many more goldfish are there than guppies?

Answer 1

You can do 3x6 and get 18, and what you have left over which is 3 that is how many guppies you have and if you do 18-3 you get 15 which is your answer

Answer 2

Lets name the number of guppies in the tank as x
number of goldfish in the tank is 6 times the amount of guppies.
since the amount of guppies is x, then number of goldfish is 6 * x = 6x

therefore total amount of guppies and goldfish is x + 6x 
there are total of 21 fish
therefore x + 6x = 21
7x = 21
x = 21/7 
x = 3
therefore number of guppies = 3 
number of goldfish -6x and x = 3 therefore  3 x 6 = 18 goldfish 
we are asked to find how many more goldfish than guppies 
we have to find the difference 
18 - 3 = 15
there are 15 more goldfish than guppies