a)
his income must be "x" which is the 100%, and we would know that 0.2% of that is 12.37.
[tex]\begin{array}{ccll} amount&\%\\ \cline{1-2} x&100\\ 12.37&0.2 \end{array}\implies \cfrac{x}{12.37}=\cfrac{100}{0.2}\implies 0.2x=1237 \\\\\\ x=\cfrac{1237}{0.2}\implies x=61.85[/tex]
b)
his income must be "x" which is the 100%, and we would know that 2% of that is 12.37.
[tex]\begin{array}{ccll} amount&\%\\ \cline{1-2} x&100\\ 12.37&2 \end{array}\implies \cfrac{x}{12.37}=\cfrac{100}{2}\implies 2x=1237 \\\\\\ x=\cfrac{1237}{2}\implies x=618.5[/tex]
btw he's not making much either way.