linarith
a b c d : ℝ
ha : 0 < a
hb : 0 < b
hc : 0 < c
hd : 0 < d
h8 : a / (a + b + c + d) < a / (a + b + d)
h9 : b / (a + b + c + d) < b / (a + b + c)
h10 : c / (a + b + c + d) < c / (b + c + d)
⊢ 0 < a + c + d
no goals