Help!! Urgent. What is in the middle of 1e+2 and 1e+3??? why doesn't 1e+2.5 exist? Help!

How do you solve a question like this?

The following division is being performed using multiplication by the reciprocal find the missing numbers is 5/12 divided by x/3 equals 5/12 times x/10 equals 1/x

On #16 : explain how factoring a trinomial, ax^2+ bx+ c, when a does not equal 1 different from factoring a trinomial when a = 1.