Answer:
5x+6y=60
Step-by-step explanation:
x= $5 per pound of second type of seed
y=$6 per pound of first types of seed
 
        
             
        
        
        
Answer:
$100
Step-by-step explanation:
8x= 160
160/8 = 20
x=20
5x = 100
 
        
             
        
        
        
Answer:
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Explanation:
Simulate (build a table) the growing of the number of pennies for some nights to figure out the pattern:
First night:          1 penny = 2⁰
Second night:    1 × 2 pennies = 2¹
Third night:        2 × 2 = 2²
Fourth nigth:      2² × 2 = 2³
nth night:           2ⁿ⁻¹
You want 2ⁿ⁻¹ ≥ 2,000,000,000
Which you solve in this way:
- n-1 log (2)  ≥ log (2,000,000,000)
- n - 1  ≥ log (2,000,000,000) / log (2)
Since n is number of days, it is an integer number, so n ≥ 32.
Hence, she will have a total of more than $ 2 billion after 32 days.
You can prove that by calculating 2³² = 2,147,483,648.