9+12=m or 9+12=21
this is because when we start with m-9=12 we know that m is supposed to be the sum of 9 and 12.
if we check our work we will see this
9+12=21
9+12=21
m-9=12
21-9=12
is already in simplest form...so it can't be simplified any further because;
99 doesn't go into 100 evenly nor could be divided by a same number. :D
You can reduce the percentages to fractions:


So, we have


A, B, and D. A trapezoid cannot be parallel because the 2 left and right sides will eventually meet/connect.