The given number is 4.125
Since there are 3 decimal places, then we can write the decimal part as a fraction with denominator 1000
[tex]4.125=4\frac{125}{1000}[/tex]Now, we can simplify the fraction by divide up and down by the same number
[tex]\begin{gathered} \frac{125}{1000}=\frac{\frac{125}{5}}{\frac{1000}{5}}=\frac{25}{200} \\ \frac{25}{200}=\frac{\frac{25}{5}}{\frac{200}{5}}=\frac{5}{40} \\ \frac{5}{40}=\frac{\frac{5}{5}}{\frac{40}{5}}=\frac{1}{8} \end{gathered}[/tex]Then the number is
[tex]4\frac{1}{8}[/tex]This is a mixed number in its simplest form
The answer is 4 1/8
[tex]4\frac{1}{8}[/tex]