I think it's frictional force, and if that's not it...then it could be the net force.
Don't really know.
21+21= 42 cookies minus 4 = 38 cookies
38/3= 12.66(round down to 12)
She made 12 bags with 3 in Each which is 36, so 2 were left over
There would have been 81 of the $7 album sold, and 78 of the other.
81x7=567
78x9=702
567+702=1269