We need to account for both x values on either side of the length, and width.
Thus, the length becomes 10 + x + x = 10 + 2x
and the width becomes 5 + x + x = 5 + 2x
For the second question, I'm assuming we don't account for the area that is covered by the garden.
Then we can say that the path is measured by: (5 + 2x)(10 + 2x) - 50, which is the area of the garden itself.
(5 + 2x)(10 + 2x) - 50 = 54
Expanding the brackets:






x = -9, or x = 3/2
Since x > 0, then x ≠ -9
Thus, the only x-value we can take is x = 3/2
Time for first plane = 625 / 250
= 2.5 hours
after 1.25 hours
boeing 747 takes 1.25 hours (2.5 - 1.25) to arrive at the same location at the same time
so, speed = distance / time
= 625 / 1.25
= 500
the average speed of the boeing 747 is 500 mph
18.386 rounded to the nearest hundredth would be 18.39