Răspuns :
3x+999 =x+3451
3x-x=3451-999
2x =2452
x=1226
verif ; 3*1226 +999 =1226+3451
3678+999 =1226+3451
4677 =4677
3x-x=3451-999
2x =2452
x=1226
verif ; 3*1226 +999 =1226+3451
3678+999 =1226+3451
4677 =4677