According to your question, there are 2 unknown numbers mentioned.
Let the 2 unknown numbers be represented by the variables x & y, then
x is considered to be one of the numbers being more than y by the addition of 4, .ie.
x = 4 + y --- (1)
The sum of the 2 numbers is 60, i.e.
x + y = 60 --- (2)
To find the smaller number, we solve eqn (1) & (2) using the concept of substitution, i.e. substitute 4 + y for x in eqn (2), i.e.
4 + y + y = 60
4 + 2y = 60
2y = 60 - 4
2y = 56
y = 28 ...Ans.
Recall that x is more than y by 4, then 28 is the smaller number.
they can each sit on floor by lining equally some can move back for example the shortest ones can sit medium tall can stand and the largest people can stand in the very back