A dozen is 12 and since 4 is a multiple of 12, I did 12 divided by 4 which is three. So i did 3.50 multiplied by 3 and the answer is 10.50
It is 3.75 for the answer
What are you converting it to/from?
The Pythagorean theorem applies to the sides of this right triangle.
... x² + (4/7)² = (5/7)²
... x² = 25/49 -16/49
... x = √(9/49)
... x = 3/7
The unknown side has length 3/7.
_____
You might recognize that this is a 3-4-5 right triangle with a scale factor of 1/7.