Determine the scale of the aerial photograph where: f=80mm, H=5500m and h=3560m. please round the answer to the nearest thousand

The focal length $f$ is given in millimeters, so convert it to meters to match the units of height.
$f = 80\ \text{mm} = 80 \times 10^{-3}\ \text{m} = 0.080\ \text{m}$

The flying height above ground level is the difference between the flying height above sea level ($H$) and the average elevation of the terrain ($h$).
$H_{\text{ground}} = H - h = 5500\ \text{m} - 3560\ \text{m} = 1940\ \text{m}$

The scale ($S$) is given by the formula $S = f / H_{\text{ground}}$.
$S = \frac{0.080\ \text{m}}{1940\ \text{m}}$
$S = 0.0000412371134$

To express the scale as a ratio of 1:X, we take the reciprocal of the calculated scale.
$X = \frac{1}{0.0000412371134} = 24250$

Rounding this value to the nearest thousand:
$24250 \approx 24000$

The scale of the aerial photograph is:
$1:24000$