fix math type in docs

docs/book/content/corp_incidence.md

@@ -45,7 +45,7 @@ The difference when running the model with a consideration of the corporate inci
 
 ### Distribution of the CIT across individual taxpayers
 
-The corporate income tax is distributed across individual taxpayers in a proportional manner.  For example, assume that 50% of the corporate income tax is borne by shareholders and that corporate income taxes paid are $50 billion.  When distributing the corporate income tax, `Tax-Brain` will change aggregate shareholder income (short-term capital gains, `p22250`, long-term capital gains, `p23250`, and dividends,`e00600`) by $ \$50 billion * 0.50 = \$25 billion$.  To allocate this $25 billion across individual taxpayers, we assume equal percentage changes across taxpayers.  Thus, taxpayers with more shareholder income have larger dollar value changes in their income.  The percentage shareholder income is adjusted by is determined as $ pct = \frac{\text{shareholder incidence} \times \text{CIT Revenue}}{\text{Aggregate shareholder income}}$.  So, continuing with our example, suppose aggregate shareholder income is $500 billion, then the percentage change in shareholder income applied to each taxpayer is $\frac{0.5 * 50}{500} = \frac{25}{500} = \frac{1}{20} = 5\%$.
+The corporate income tax is distributed across individual taxpayers in a proportional manner.  For example, assume that 50% of the corporate income tax is borne by shareholders and that corporate income taxes paid are \$50 billion.  When distributing the corporate income tax, `Tax-Brain` will change aggregate shareholder income (short-term capital gains, `p22250`, long-term capital gains, `p23250`, and dividends,`e00600`) by \$50 billion $\times$ 0.50 = \$25 billion.  To allocate this \$25 billion across individual taxpayers, we assume equal percentage changes across taxpayers.  Thus, taxpayers with more shareholder income have larger dollar value changes in their income.  The percentage shareholder income is adjusted by is determined as $ pct = \frac{\text{shareholder incidence} \times \text{CIT Revenue}}{\text{Aggregate shareholder income}}$.  So, continuing with our example, suppose aggregate shareholder income is \$500 billion, then the percentage change in shareholder income applied to each taxpayer is $\frac{0.5 * 50}{500} = \frac{25}{500} = \frac{1}{20} = 5\%$.
 
 Analogous adjustments are made to wage income (`e00200`, `e00200p`, `e00200s`) and other capital income, which is made up of:
 * Taxable interest: `e00300`