$\fraction{3 a}{b} = c$
Solve for a
Solve for b

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3a=cb
Multiply both sides of the equation by b.
3a=bc
The equation is in standard form.
\frac{3a}{3}=\frac{bc}{3}
Divide both sides by 3.
a=\frac{bc}{3}
Dividing by 3 undoes the multiplication by 3.
3a=cb
Variable b cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by b.
cb=3a
Swap sides so that all variable terms are on the left hand side.
\frac{cb}{c}=\frac{3a}{c}
Divide both sides by c.
b=\frac{3a}{c}
Dividing by c undoes the multiplication by c.
b=\frac{3a}{c}\text{, }b\neq 0
Variable b cannot be equal to 0.