A+B+C=61,A+C+D=71,A+B+D=62,B+C+D=64.求A、B、C、D各是多少

A+B+C=61 ①A+C+D=71 ②A+B+D=62 ③B+C+D=64 ④由①+②+③得3A+2B+2C+2D=194 ⑤由⑤-④×2得3A=66A=22由②-③得C-B=9 ⑥由①+⑥得22+2C=70C=24代入⑥得B=C-9=15由④得D=64-B-C=64-15-24=25所以A=22 B=15 C=24 D=25...