this is difficult for me...

To find the length in feet of each board, we need to convert the length of each board from feet and inches to just feet.

Since 9 inches is equal to 3/4 of a foot (since there are 12 inches in a foot), we can write the length of each board as 2 feet + 3/4 of a foot. This can also be written as 2 + 3/4.

To multiply a whole number by a fraction, we can convert the whole number to a fraction with a denominator of 1. So 2 can be written as 2/1.

Now we can multiply the fractions: (2/1) multiplied by (3/4). When multiplying fractions, we multiply the numerators (2 x 3) to get the new numerator, and multiply the denominators (1 x 4) to get the new denominator. This gives us 6/4.

The fraction 6/4 can be simplified by dividing both the numerator and the denominator by their greatest common factor, which is 2. Dividing both 6 and 4 by 2 gives us 3/2.

Now we have the length of each board in feet as 3/2.

To find the total amount of board feet the carpenter needs, we multiply the number of boards (4) by the length of each board in feet (3/2).

4 multiplied by 3/2 is equal to (4/1) multiplied by (3/2). Multiplying the numerators (4 x 3) gives us 12, and multiplying the denominators (1 x 2) gives us 2. So the result is 12/2, which simplifies to 6.

Therefore, the carpenter needs to buy 6 feet of wood in total.

I hope this explanation helps you understand how to get the answer!