Răspuns :
x- prima zi
y- a doua zi
z-ultima zi
x+y+z=81
inlocuim: x+ (2x+ 3)+ 15=81
3x+3+15=81/-15
3x+ 3= 66/-3
3x=63/:3
x=21-prima zi
Y= 21 ori 2+ 3= 45- a doua zi
y- a doua zi
z-ultima zi
x+y+z=81
inlocuim: x+ (2x+ 3)+ 15=81
3x+3+15=81/-15
3x+ 3= 66/-3
3x=63/:3
x=21-prima zi
Y= 21 ori 2+ 3= 45- a doua zi