First of all, you can simplify the 4 at the numerator and the 14 at the denominator (they're both multiple of 2):

Now, rationalize a denominator means that you have to get rid of the square root, in order to have an integer denominator.
To do so, remember that you can always multiply any number by 1 without changing its value, and you can always think of 1 as a fraction where numerator and denominator are equal:

7033/10000 is the answer you're looking for
To determine the number of cubes he needs to fill the box (this is assuming the cubes are 1 in cubes, he would need to calculate the volume of the box. To find the volume he would multiply the length by the width by the height. This would be 5 in x 6 in x 7 in. The volume is 210 cubic inches, so he could fill it with 210 one inch cubes.
Answer:
100 ft squared
Step-by-step explanation: you would usually round up to the nearest whole number with these and 9.7 would round to 10 and 10 times 10 would be 100