Question 35830
I'm assuming that you would like to factor this?
15cd-16+12c-20d 


Rearrange the terms and group the first two and the second two terms together:

15cd+ 12c - 20d - 16


From the first two terms take out a common factor of 3c, and from the second two terms take out a common factor of -4, and hope for the best--a common factor must result, or this doesn't work!!

15cd+ 12c - 20d - 16
3c(5d+ 4) -4(5d+ 4)  


Glory Hallelujah!!  We must be living right!!  We DO have a common factor of (5d+4).


Take out the common factor of (5d+4):

(5d+4)(3c-4)


R^2 at SCC