Guppies . . . . 1 time
Tetras . . . . . 11 times
Sum of fish. . . . . 12 times
Number of fish . . 48
12 times = 48
Divide each side of the equation by 12 :
1 time = 4
Guppies = 1 time = 4 guppies
Tetras = 11 times = 11 x 4 = 44 tetras
Total fish = 4 + 44 = 48 yay !