Răspuns :
7 / 8 = ( 2 - a + 1 ) / 5
8 × ( 2 - a + 1 ) = 7 × 5
16 - 8 a + 8 = 35
16 - 8 a = 35 - 8
16 - 8 a = 27
8 a = 16 - 27
8 a = - 11
a = - 11 / 8
7 / 8 = ( 2 - a + 1 ) / 5
8 × ( 2 - a + 1 ) = 7 × 5
16 - 8 a + 8 = 35
16 - 8 a = 35 - 8
16 - 8 a = 27
8 a = 16 - 27
8 a = - 11
a = - 11 / 8