drum = "a" lungime
prima zi=18 km
rest = a- 18
a doua zi 3 pe 5 ×( a-18 ) = 3· ( a -18 ) /5= ( 3a - 54 ) / 5
rest = ( a -18 ) - 3×( a-18) / 5 =2×(a-18)/5
2 ×( a-18 ) / 5 = 25%×a
2 × ( a - 18 ) / 5 = 25 × a /100 = a / 4
2 ×4 × ( a -18) = 5a
8a - 8 × 18 =5a
8a - 5a = 8 × 18
3a= 8 ×18
a= 8 × 18 :3 = 8 ×6 km = 48 km
apoi muchiile ⇒ x , y,z
4x+ 4y + 4z = 60 cm
60: 4 =15 cm
x + y + z =15cm
