Question 902929
Work within grouped expressions first.  You can treat each of those grouped expressions separately first.


{{{9*(3/4)/(-9/20)}}}


The fraction bar IS another grouping symbol.  The lowest common denominator for this ...?  No... better, the way you divide by a fraction is to multiply by its reciprocal.


{{{(9*(3/4))(-20/9)}}}


Now you can group the numerator factors and group the denominator factors, separately:


{{{(9*3*(-20))/(4*9)}}}


Cancel any redundant factors of 1.


{{{(9*3*(-1)(4*5))/(4*9)}}}


{{{(-3*5)}}}


{{{highlight(-15)}}}