Last Question
Because this may not be the question you want, I'll omit the first step which should be done with latex. The key to all of these except C is to invert the second fraction (turn the second fraction upside down) and multiply.
A
=(6*-2) / (5*3) = - 12/15 = -4/5
B
= (7*5) / (4*3) = 35 / 12 = 2 11/12
C
Impossible to do 4/0 cannot be done.
D
= (-2*-4)/(3*5) =
8/15