-3b / 8
Explanations:The given expression is:
[tex]\frac{3}{8}b\text{ - }\frac{3}{4}b[/tex]Which can be re-written as:
[tex]\frac{3b}{8}-\frac{3b}{4}[/tex]Note that the LCM of 8 and 4 is 8
Therefore, the expression can be simplified as:
[tex]\begin{gathered} \frac{3b-2(3b)}{8} \\ \frac{3b-6b}{8} \\ \frac{-3b}{8} \end{gathered}[/tex]The simplified expression is -3b/8
