Because none of those are the right answer. you are given units in feet in the diagram. but are told 6 inches are lost in 4 hours. so you multiply length width and height keeping the feet then subtract .5 ft. the equation should look like V=(12×7×8)-.5
So if you have 30 oil, 24 photos, 21 sketches, the first thing I notice is that all of these numbers are divisible by 3. Since there are no specifications of how many rows for each category. You can divde the 30/10, 24/8, and 21/7 you would have 10 rows oil, 8 rows of photos, and 7 rows of sketches. In short, I believe your answer should be 3.
Hope this helps! Sorry if this explanation is unclear, please feel free to ask questions. <3
X=12
First you would combine like terms 7+3=10
Then you would have 10 +5x =70
Subtract 10 from both sides 10-10 & 70-10
That will leave you with 5x=60
Divide 5 from both sides 5x/5 & 60/5
Answer will be x = 12
