9/10-1/5=7/10 weight of second fish
9/10+7/10=16/10 kg=1.6 kg
or you can just translate everything into decimals
9/10=0.9 kg
1/5=0.2 kg, then
0.9-0.2=0.7 kg weight of the second fish
0,9+0,7=1.6 kg the weight of the two fish = 1кг600г
Первое 312500
второе 203500