how did we get 67% of all branches taken??

Branches occur with a frequency of 14% to 16% in integer programs and 3% to 12% in floating point programs.
About 75% of the branches are forward branches
60% of forward branches are taken
80% of backward branches are taken
67% of all branches are taken

Ignore the first part. Those ranges will confuse you. Fortunately, they have nothing to do with the calculation. Without any information concerning the relationship between integer and floating point programs, there is no rational way to weight these values.

0.75 * 0.60 + (1-0.75) * 0.80 = 0.75 * 0.60 + 0.25 * 0.80 = 0.45 + 0.20 = 0.65

I would have to take exception to the 67% value. It appears to be 65%