In order to follow Susan's specifications, 9 pegs will fit on the board.
Work Step by Step
The board Susan is $so$ specific about must be 4 ft. long. This is the same as 48 inches. There must be 6 inches of space on each end of the board, so this automatically reduces the space we can put pegs on from 48 in. to 36 in. There must be 4 inches between each peg, so 36 must be divided by 4. This gives us our answer of 9 pegs.