It wont be -7/10 because to change a mixed number to an improper fraction, we multiply the whole number by the denominator and then add this product with the numerator.
We know the width is not long enough to lay the picnic table across, as it is only 5 2/3 ft. wide. We can see if the other side is long enough by dividing the product of the two sides by the side we know.
36 5/6 divided by 5 2/3 = 6 1/2 ft. which is not long enough to house a 7 ft. long picnic table without going diagonal.
