Basically, it's line 60 (tax) + SS+Medicare taxes paid (the full 14.2%) / line 43 (taxable income -- not AGI).
Which is to say all the huffing and puffing boils down to him not paying SS/Medicare on the 60 million in capital gains and dividends.
Well, that and the 14.2% ss/medicare tax is applied before any deductions and credits so an individual with a $100,000 salary, $14,200 in FICA taxes, $85,800 in deductions (that's a lot of kids) and $1,500 in income tax has a 110% tax rate, according to his "math".
Worth noting -- as of 2013, there's a 3.8% medicare tax on investment income in excess of $250,000.
Even if you count both halves of SS and Medicare, the legit way of doing it is (income tax + employee’s payroll tax + employer’s payroll tax) / (gross pay + employer’s payroll tax). You have to count the employer’s side in addition to the gross pay because it is part of the total pay and benefits. Counting the employer’s payroll tax only in the numerator is crooked. Dividing by the pay after deductions and exemptions is outright intellectual fraud. You might as well just make up a number.