First do 10x7 =70
Since there’s 4 sides with this measure mentally do 70x8=560
560
10x8.7=87
87+560=647
647sq feet
Answer:
1) 
2) 
Step-by-step explanation:
1)

Subtract 15 from both sides

Divide both sides by 2




this shows that 10 is the right answer
2)

Add 3 to both sides

Divide both sides by 7




this shows that 3 is the right answer
Hope this helps
If every shelf has the same amount of books, then it can be seen as proportional because one shelf has 43 and 2 have 86, and it keeps going up in a consistent way.
so 43/1 = 86/2 .
Happy studying ^-^
Answer:
You can always ask the tutor they give the correct answer :))