The answer is 6/9 or 2/3 because 2X2X2=8 and 9X9X9=729......it equals 8/729
The answer would be "Nine students each make 2 models of Mars and its moons. How many models did they make in total?" Since the answer is 18 and there are 9 students (and also since 18 can be divided into 9), you can divide 18 and 9 to get 2. This makes sense because if each student makes 2 models (as stated), there'd be a total of 18 models (as stated in the question you gave). Hope this helped!
For every c substitute 4 and for every d substitute -2
c=4
d=-2
6c + 5d - 4c - 3d + 3c - 6d
= 6(4)+ 5(-2)- 4(4)- 3(-2)+ 3(4)- 6(-2)
=24+(-10)-16-(-6)+12-(-12)
=24-10-16+6+12+12
=28
