i haven't done math in a year and a half, but im sure that this is the answer.
So, for a perimeter of a square its adding all the sides, so if you know that the perimeter is 48, you can divide it by 4. You get all the sides to be 12. Then mulitply it by .75 and get nine.
48÷4= 12
12·.75= 9
each side would be nine