Respuesta :
set 4 is the correct answer because if you multiply 10 by 10 + 20 times 20, you will get 400 and when you multiply 30 by 30 you also get 400 which is equal to 400 there for you answer would be set 4.
Hope I helped if I did click the thx button ;)
Hope I helped if I did click the thx button ;)