With system of linear equation in 2 variables, blue fish in the aquarium are 20 fish.
To begin this system of linear equation in 2 variables, we need to define the variables. Let's say:
Red fish : x
Blue fish : y
Red fish = Blue fish + 10
x = y + 10
x - y = 10 (1)
Red fish = 60% all fish
Red fish = 60% (red fish + blue fish)
x = 60% (x + y)
x = 3/5 (x + y)
5x = 3(x + y)
5x = 3x + 3y
5x - 3y - 3x = 0
2x - 3y = 0 (2)
After we got 2 equation, we ready to find each of the variable.
x - y = 10
2x - 3y = 0
Let's do elimination. First we need to make one variable has same coefficient in both equations. So we multiply the first equation with 2.
x - y = 10 ---> x2
2x - 3y = 0 ---> x1
Eliminate the same coefficient variable in both equations.
2x - 2y = 20
2x - 3y = 0 -
0 + y = 20
y = 20
After we know one variable, just substitute it in one equation. In this case substitute y = 20 in first equation.
x = y + 10
x = 20 +10
x = 30
Red fish = x = 30
Blue fish = y = 20
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