In this problem, \(a\), \(b\), \(c\), and \(d\), are nonzero integers If \({{a} \over b} \) is added to \(x\), the sum is \({{c} \over d}\). Which statement can be used to prove that \(x\) must be a rational number?
a) \(x = {{c-a} \over d-b}\)
b) \(x = {{c+a} \over d-b}\)
c) \(x = {{cb-ad} \over bd}\)
d) \(x = {{cb+ad} \over bd}\)
