Klaus was replacing the roof on his house. he used 420 nails to attach all the pieces of wood. each piece of wood needed 7 nails to hold it in place. he used 40 piece es of wood. how many pieces were left?

20

Step-by-step explanation:

if 7 nails are required for each piece of wood, you must determine how much wood you have in total by dividing the amount of nails by 7.

If you have used 40 nails out of sixty, you 20 left because

60-40=20