Math problem in the third grade of primary school: Mei Mei and I weigh 30 kilograms, Mingming weighs 25 kilograms, and Gong Hong weighs 35 kilograms. How many kilograms do Meimei and Gong Hong weigh r
Math problem in the third grade of primary school: Mei Mei and I weigh 30 kilograms, Mingming weighs 25 kilograms, and Gong Hong weighs 35 kilograms. How many kilograms do Meimei and Gong Hong weigh respectively?
Let a, b, c and d in turn.
Then a+b=30 ①
a+c=25 ②
a+d=35 ③
①-②=b-c=5 ④。
①-③=b-d=-5 ⑤
②-③=c-d=- 10 ⑥
Then B = 15, C = 10 and D = 20. A = 15。