Răspuns :
[(n*5+9999)*6]+18920=87374
(n*5+9999)*6=87374-18920
(n*5+9999)*6=68454
n*5+9999=68454:6
n*5+9999=11409
n*5=11409-9999
n*5=1410
n=1410:5
n=282
(n*5+9999)*6=87374-18920
(n*5+9999)*6=68454
n*5+9999=68454:6
n*5+9999=11409
n*5=11409-9999
n*5=1410
n=1410:5
n=282
y×5+9999=y×6+18920=87374
5y+9999= 6y+18920=87374
6y-5y+18920-9999=87374
y+8921=87374
y=87374-8921
y=78453