Question 182979
5xy - 3yz - 5xz + yz - 4xz + 7xy
First combine all like terms:
(5xy+7xy)+(yz-3yz)-(5xz+4xz)
12xy-2yz-9xz
Now replace the x,y & z terms with their numeric values:
and evaluate it for x = 10, y = -4, z = -6. 
12(10*-4)-2(-4*-6)-9(10*-6)
12*-40-2*24-9*-60
-480-48+540=12 ans.