Min and Mary have some biscuits each. If Min gives Mary 12 biscuits, Min will have ⁷₈ as many biscuits as Mary. If Min gives Mary 2 biscuits, they will have an equal number of biscuits. How many biscuits does Min have at first?

	Case 1		Case 2
	Min	Mary	Min	Mary
Before	7 u + 12	8 u - 12	7.5 u + 2	7.5 u - 2
Change	- 12	+ 12	- 2	+ 2
After	7 u	8 u	7.5 u	7.5 u

Total number of biscuits that Min and Mary have
= 7 u + 8 u
= 15 u 

Number of biscuits that Min and Mary each has in the end is the same.

Number of biscuits that Min and Mary each has in the end in Case 2
= 15 u ÷ 2
= 7.5 u

Number of biscuits that Min had at first is the same in Case 1 and Case 2.

7.5 u + 2 = 7 u + 12
7.5 u - 7 u = 12 - 2
0.5 u = 10

1 u = 10 ÷ 0.5 = 20

Number of biscuits that Min has
= 7 u + 12
= 7 x 20 + 12
= 140 + 12
= 152

Answer(s): 152