Maya wants to mark a length of 7 inches on a sheet of paper, but she does not have a ruler . she has pieces of wood that are 4 inches 5 inches, and 6 inches long. explain how she can use these pieces to mark a length of 7 inches.

Ok
6+1=7
if only we could find 1
hmm

4+1=5
so mark a starting line
put the 4 inch and 5 inch wood at that line, facing the same direction (lying flat on paper)
the difference between the pieces of wood is 1 inch
mark the end of the 5 inch and the end of the 4 inch
that is 1 inch
now pick either end of that 1 inch mark and measure 6 inches more