If a/7 = b/7 = c/8 then find ( (a + b )/(a + b + c ) ).

Given, \(\frac{a}{7}\) = \(\frac{b}{7}\) = \(\frac{c}{8}\)

Here we can directly conclude that 

a = 7, b = 7, c = 8, hence

⇒ (\(\frac{a + b }{a + b + c }\)) = (\(\frac{7 + 7 }{7 + 7 + 8 }\)) = \(\frac{7}{11}\)