The foci of an ellipse are (c,0) & (-c,0)
Where c² = a² - b²
The major axis is 34 feet
So 2a = 34
Dividing by 2 on both sides
a = 17
Also minor axis is 16 feet
So 2b = 16
Dividing by 2 on both sides
b = 8
Now we know
c² = a² - b²
c² = 17² - 8² = 289 - 64 = 225
Taking square root on both sides
c = 15 feet
Now the two foci are (15,0) & (-15,0)
Distance between these points is 15 - (-15) = 15 + 15 = 30
The distance between the two foci is 30 feet.