Answer:
2 books
Step-by-step explanation:
If 7 books= 1 box
Then 30 books= 30÷7= 4 boxes with a remainder of 2 books
Therefore books left over= 2 books
x=0
x=3
3+x=2x
Subtract x from each side to get the variable on one side
3+x-x=2x-x
3 = x