Calculate angle ACB.

Solution:

The image shows a right-angled triangle ABC, where the angle at B is 90 degrees. The angle at A is given as 54 degrees.

The sum of angles in a triangle is always 180 degrees. Therefore, in triangle ABC:

\( \angle A + \angle B + \angle C = 180^{\circ} \)

We are given:

\( \angle A = 54^{\circ} \)

\( \angle B = 90^{\circ} \)

We need to find \( \angle C \).

Substitute the known values into the equation:

\( 54^{\circ} + 90^{\circ} + \angle C = 180^{\circ} \)

Combine the known angles:

\( 144^{\circ} + \angle C = 180^{\circ} \)

To find \( \angle C \), subtract 144 degrees from 180 degrees:

\( \angle C = 180^{\circ} - 144^{\circ} \)

\( \angle C = 36^{\circ} \)

Therefore, angle ACB is 36 degrees.

Ответ: \( 36^{\circ} \).