The total weight will be the sum of the weights of the bags present. The weight of t bags of topsoil will be 30t; the weight of m bags of mulch will be 30m. We want the total weight to be at most 330. (Weight numbers are in pounds.)
30t +30m ≤ 330
We can remove a factor of 30 to simplify this to ...
t + m ≤ 11
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You may be expected to use the un-simplified form of the inequality.
D) 4s-10 would be the correct expression. To get the perimeter of the rectangle you would get the expresssion: (s-6)+(s-6)+(s+1)+(s+1), simplified this is equal to 4s-10.
