maths

你好!

3A+2B=78
2A+3B=72

6A+4B=156
6A+9B=216

so that

5B=60
B=12

When B=12,
3A+24=78
3A=54
A=18

這題數可以用聯立方程來計算。

A+A+A+B+B = 78
3A+2B = 78
3A = 78-2B
A = 78-2B/3 ......(1)

A+A+B+B+B = 72
2A+3B = 72 ......(2)

把(1)代入(2)，可得，
2(78-2B/3)+3B = 72
(156-4B/3)+3B = 72
3[(156-4B/3)+3B] = 3(72)
156-4B+9B = 216
156+5B = 216
5B = 60
B = 12

把B = 12代入(1)，可得，
A = 78-2(12)/3
A = 78-24/3
A = 54/3
A = 18

A+A+A+B+B=78
A+A+B+B+B=72

A=18
B=12