How to divide fractions and do fractions

To fractions you keep the first fraction change the sign to a multiplication sign and flip the second fractions for example: 1/2 / 3/4 = 1/2 x 4/3 = 4/6 = 2/3

You divide fractions like for example;
3/4 divide 5/3       1) Set up equation
3/4 multiply 3/5     2)  Keep(don't change first fraction) Change(Change                                                     operation to opposite operation) Flip (denominator to                                            numerator and numerator goes to denominator)
                                     
Then Solve like numerator w/ numerator  and denominator w/ denominator
3/4 divide 5/3 equals 9/20

If the diameter is 8 than the radius is 4 because 2r or 2*radius equals the diameter. 4*2=8. 8/2=4.