How do you solve $\dfrac{a}{{15}} = \dfrac{4}{5}$?

Hint:
Here we need to proceed by using just the simple and easy method where we just need to know that when we take the term from one side of to the other side the sign changes. The sign becomes and multiplication changes to division. By using this rule we can easily find here the value of the required variable which is $a$.

Complete step by step solution:
Here we are given the equation where we need to find the variable $a$ from the given equation which is $\dfrac{a}{{15}} = \dfrac{4}{5}$
So in order to solve this we just need to know that when we take the term from one side of to the other side the sign changes. The sign becomes and multiplication changes to division. By using this rule we can easily find here the value of the required variable which is $a$
For example: If we have the term say $x - 4 = 6$ and we need to calculate the value of $x$
Here when we will take the term $4$ from LHS to RHS the sign of $4$ which is negative will change to positive and will become $x = 6 + 4 = 10$
Similarly we will apply for division changing to multiplication.
Now we have the equation as:
$\dfrac{a}{{15}} = \dfrac{4}{5}$
Taking $15$ from left hand side to right hand side, we can say that as it is dividing the term $a$ but on the RHS it will multiply the term $\dfrac{4}{5}$
So we will get:
$\dfrac{a}{{15}} = \dfrac{4}{5}$
Now we can write it as:
$a = \dfrac{4}{5} \times 15$
Now we need to find the value of $a$so we can solve it further and we will get:
$a = \dfrac{4}{5} \times 15 = 4 \times 3 = 12$

Hence we get $a = 12$

Note:
Here the student must know that as the sign changes when we move from LHS to RHS or from RHS to LHS, in the similar way the power also changes:
If we are given ${a^n} = b$ then we can write that $a = {b^{\dfrac{1}{n}}}$