The correct answer would be:
"I'll place the crutches about 6 inches to each side."
This is called tripod position. In order to achieve a correct position, one must in a certain body position. Crutches should be six inches apart from both sides. Crutches should be between one and two inches below one’s armpits, while a person is standing straight, while handgrips should be in line with one’s hips.
This could be a case of Obsessive-Compulsive Disorder (OCD) considering people with this condition have the urge to do certain things repeatedly as a way of banishing the scary thoughts or making sure they are safe or even clean.
The total amount would be 19cm. this is because you add 9+4+6.