fie a lungimea drumului
in prima zi Andra parcurde 1/3 din a => a/3
in a doua zi Andra parcurge 1/3 din (a- a/3) => 1/3 * a - 1/3 * 1/3 = a/3 - 1/6 = 2a/6 - 1/6 = 2a-1/6
in a treia zi Andra parcurge 48 km.
a= a/3 + 2a-1/6 + 48 => 6a= 2a + 2a - 1 + 288 => 6a= 4a + 287 => 2a= 287 => a=144