La 4 va rog multt, repedee
Dau coroana

x₁ = x+20%x = x+ 20x/100 = x+x/5 = 6x/5
x₂ = x₁-y%x₁ = 6x/5 - (y/100)(6x/5) = (600x-6xy)/500
600x-6xy = 500x <=> 100x = 6xy => y% = 100x/6 = 16,67%