Question

Let a=3/4 and b=1/5. If a*x=b, then what is x?

Answer 1

In general, any equation like $ax=b$ (assuming $a \neq 0$) is solved by

$x= \dfrac{b}{a}$

So, in your case, the solution is

$x = \dfrac{\frac{1}{5}}{\frac{3}{4}}$

Dividing by a fraction means to multiply by the inverse of that fraction:

$\dfrac{\frac{1}{5}}{\frac{3}{4}} = \dfrac{1}{5} \cdot \dfrac{4}{3} = \dfrac{4}{15}$