@deriniko9 Three Shaggys weigh 90 kg:
3H = 90
H = 30 kg
Two Shaggys and one Fred weigh 80 kg:
2H + F = 80
2(30) + F = 80
F = 20 kg
Two Scoobys and one Fred weigh 100 kg:
2S + F = 100
2S + 20 = 100
2S = 80
S = 40 kg
Answer: Scooby-Doo weighs 40 kg. πΆ