Question

$\frac{7}{12} a + \frac{3}{12} a$
если а=12
$\frac{4}{7} a + \frac{6}{7} a$
если а=-7

Answer 1

7/12 а + 3/12 а = а(7/12 + 3/12) = а * 10/12 = 12 * 10/12 = 10 
4/7 а + 6/7 а = а(4/7 + 6/7) = а * 10/7 = -7 * 10/7 = -10