Question

甲班和乙班共82人,乙班和丙班共86人,丙班和丁班共88人.甲班和丁班共多少人?

Answer 1

设,甲=a 乙=b 丙=c 丁=d

(1). a + b = 82

(2). b + c =86

(3). c + d =88

求 a + d = ?

(3) - (2) = d - b = 2 (4)

(4) + (1) = a + d = 84