Call x the number of campers on the low trail and y the number of campers on the high trail.
So we have
x + y ≤ 30
x ≥10
y ≥ 5
This has many solutions....(10, 20) (11, 19) (12, 18) ( 13, 17).....etc.......(24,6) (25, 5)
We can graph this...but there will be many "solution" points that aren't whole numbers - and thus - aren't really a part of the solution set because we can't have "part" of a person !!!
The 'graph' is here........https://www.desmos.com/calculator/mxbludbhfr
Tthe solution set lies along the "hypoteneuse" of the grey triangle in the middle of the graph and consists of the points in which x and y are both whole numbers !!!