To find the values of b that make the statement true you solve the equation for b:
Multiply both sides of the equation by b:
[tex]\begin{gathered} b\cdot\frac{7}{30}=b\cdot\frac{28}{b} \\ \\ b\cdot\frac{7}{30}=28 \end{gathered}[/tex]Multiply both sides of the equation by 30/7
[tex]\begin{gathered} b\cdot\frac{7}{30}\cdot\frac{30}{7}=28\cdot\frac{30}{7} \\ \\ b=\frac{28\cdot30}{7} \\ \\ b=\frac{840}{7} \\ \\ b=120 \end{gathered}[/tex]Then, the values that make the statement true are: 840/7 and 120