/*
小红 a
小明 b

b-(a-b) = 1/3 * a ①
a+(a-b)= 3 * b-30 ②


b-a+b=1/3 *a => 2b=4/3a  => 4b=8/3a  ③

2a-b=3b-30 =>               4b=2a+30 ④

8/3a=2a+30   => 8/3a-2a=30 =>8a-6a=90 => 2a=90 => a=45


带回 ③ b=30

答：小红45岁，小明30岁
*/