If a^2−b^2=2640 and a^2+b^2=6338 then what is the value of 23ab?

Question

If
a/b = 21/34;
b/c = 121/120;
c/d = 17/77;
e/f = 11/15
and
d/e = 14/17
then what is the value of
(abc/def)*2?

Answer 1

a²−b²=2640 ___________________(i)
a²+b²=6338___________________(ii)

(i)+(ii) →
2a² = 8978
=> a = 67

(i)+(ii) →
2b² = 3698
=> b = 43

23ab = 23*67*43 = 66263

Answer 2

66263

67*43*23