$1,2,3,4,6,8,12,24$ are the factors of $24$
$1,2,3,4,6,9,12,18,36$ are the factors of $36$
Common factors of $24$ and $36$ are $1,2,3,4,6$ and $12$
$HCF=12$
Now dividing both numerator and denominator by $12$
$=24÷12/36÷12$
$=2/3$
Thus $2/3$ is the equivalent factor to $24/36$.