Answer: Jenny's aunt should buy 4 pounds of pecans.
Step-by-step explanation:
Let x represent the number of pounds of almonds that Jenny's aunt should buy.
Let y represent the number of pounds of pecans that Jenny's aunt should buy.
She wants to buy 6 pounds of nuts. This means that
x + y = 6
If almonds cost $7 per pound and pecans cost $9 per pound and she wants to spend $50, it means that
7x + 9y = 50- - - - - - - - - - - - -1
Substituting x = 6 - y into equation 1, it becomes
7(6 - y) + 9y = 50
42 - 7y + 9y = 50
- 7y + 9y = 50 - 42
2y = 8
y = 8/2
y = 4
x = 6 - y = 6 - 4
x = 2
