If you would like to know how many of each type of fish did Carlos buy, you can calculate this using the following steps:
x ... the number of angelfish
y ... the number of parrotfish
405 tropical fish bought
8 times as many parrotfish as angelfish ... 8 * y = x
405 = x + y
405 = 8 * y + y
405 = 9 * y
y = 405 / 9
y = 45 parrotfish
x = 8 * y = 8 * 45 = 360 angelfish
The correct result would be 45 parrotfish and 360 angelfish.