Răspuns :
a+(a+10)+(a+10×2)+(a+10×3)=120
4a+60=120
4a=120-60
4a=60⇒a=15
a=15 km parcursi in prima zi
15+10=25 km parcursi in a doua zi
25+10= 35 km parcursi in a treia zi
35+10=45 km parcursi in a patra zi
verificare 15+25+35+45=120⇒120=120 km
..
I — prima zi
II — a doua zi
III — a treia zi
IV — a patra zi
I + I + 10 + I + 20 + I + 30 = 120 = >
4I = 120 — 60 = >
4l = 60 =>
I = 60 : 4 = >
I = 15 km
II = 15 + 10
II = 25 km
III = 15 + 10 + 10
III = 25 + 10
III = 35 km
IV = 15 + 10 + 10 + 10
IV = 25 + 10 + 10
IV = 35 + 10
IV = 45 km
I — prima zi
II — a doua zi
III — a treia zi
IV — a patra zi
I + I + 10 + I + 20 + I + 30 = 120 = >
4I = 120 — 60 = >
4l = 60 =>
I = 60 : 4 = >
I = 15 km
II = 15 + 10
II = 25 km
III = 15 + 10 + 10
III = 25 + 10
III = 35 km
IV = 15 + 10 + 10 + 10
IV = 25 + 10 + 10
IV = 35 + 10
IV = 45 km