IDK so so so sorry i am not fameluar with this
Since the beacons rotate together, the angular speed is constant.
From the time you see the first beacon, you have to wait for the lighthouse to make 120°, i.e. 1/3 of a whole turn.
So, if T is the time it takes for the lighthouse to make a whole turn, the interval between the first and the second beacon is T/3.
The interval between the second and third beacon is the amount of time it takes to the lighthouse to make the remaining 2/3 of a turn, so that you'll see the first beacon again. So, this time is 2T/3
So, the ratio is

So, the time between the second and third beacon is twice as much the time between the first two.
The value of 28 tens is basically doing 28 times 10(in case you didn't know). 28 times 10 is 280. So the value of 280 tens is 280.
Answer:
1)





2)

Multiply
:

Apply Difference of Squares formula: 





a = 5, b = -2