Answer:
we want a number between 50 and 80 that has exactly 4 factors, where one is 2.
this means that our number X can be written as:
X = 2abc
where a, b and c are numbers that we do not know. We can start giving those numbers different values, and then changing them to get in the desired range:
X = 2357
i used the first 4 primes here,
X = 1037 = 307 = 210
this is too big, let's reduce obviously we must reduce the 7, let's change the 7 for a 3
X = 2353 = 109 = 90
We are still a little bit off, let's change the 5 for a 3.
X = 2333 = 6*9 = 54
nice, we have found a number between 50 and 80 where the factors are 2 one time and 3 three times.
