Answer: 6/5
Explanation:
Let's say Leo's initial number size is x.
Now, multiply by six-fifth
6/5x > x
Since numerator is bigger the denominator (6 > 5)
If we multiple with four-fourths 4/4x = x(no increase)
Hence "The multiplication of a number with a bigger numerator of a fraction will cause it to increase thus he could have multiplied with six-fifth".
Hope this helped!