Răspuns :
[tex]a - \frac{2a}{5} - [(a - \frac{2a}{5}):2 + 2] = 7 \\ \\ a - \frac{2a}{5} - ( \frac{3a}{5} \times \frac{1}{2} + 2) = 7 \\ \\ 10a - 4a - \frac{3a}{10} - 2 = 7 \\ \\ 3a = (7 + 2) \times 10 \\ \\ a = \frac{90}{3}= 30 \: km [/tex]
a = > lungimea traseului
2/5 din a = > 2a/5 lungimea parcursa in prima zi
(a - 2a/5) : 2 + 2 = 3a/5 : 2 + 2 = 3a/10 + 2 lungimea parcursa a doua zi
2a/5 + 3a/10 + 2 + 7 = a
2a/5 + 3a/10 + 9 = a /x10
4a + 3a + 90 = 10a
90 = 10a - 7a
90 = 3a
a = 90 : 3 = 30
Lungimea traseului = 30 km
I zi => 2x30/5 = 60/5 = 12 km
II zi = > 3 x 30/10 + 2 = 90/10 + 2 = 9 + 2 = 11 km
III zi = 7 km