Consider the TRS R consisting of the rewrite rules

1: f(x) -> s(x)
2: f(s(s(x))) -> s(f(f(x)))

There are 2 dependency pairs:

3: F(s(s(x))) -> F(f(x))
4: F(s(s(x))) -> F(x)

Consider the SCC {3,4}.
By taking the polynomial interpretation
[f](x) = [F](x) = [s](x) = x + 1,
the rules in {1,2}
are weakly decreasing and
the rules in {3,4}
are strictly decreasing.
Hence the TRS is terminating.