Zunächst Gleichungen aufstellen:
1. H + K = 42 => H = 42 - K
2. K + L = 48 => L = 48 - K oder K = 48 - L
3. H + L = 44 => H = 44 - L
H + K = 42
=> 44 - L + 48 - L = 42
=> 92 - 2L = 42
=> 50 = 2 L
=> 25 = L
K + L = 48
=> K = 48 - 25
=> K = 23
H + K = 42
=> H = 42 - 23
=> H = 19