Answer:
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His error is in step 3. The variable x is being multiplied by -7 and therefore he should have divided both sides by -7, not 7 as he did.
Answer:
Volume: 864
Surface Area: 684
Step-by-step explanation:
Volume:

Surface-Area: (Pretty Self-explanatory)
1. Triangles - 12 * 9 = 108 (You don't need to divide it by two, just leave it as is because there are two of these triangles.)
2. Base - 16 * 9 = 144
3. Height/Base - 12 * 16 = 192
4. 15 * 16 = 240
192 + 144 + 108 + 240 = 444
The Surface Area is 684.
Answer: 446.66
Explanation:
The formula for perimeter is 2 x length +2 x width
So you multiply 175.33 which gives you 350.66 and add it to 96 which gives you 446.66