Let x be the number of kiwis that Serena can buy.
The cost of 3 oranges is 3 × $0.85 = $2.55
The cost of x kiwis is x × $0.50 = $0.50x
The total cost of 3 oranges and x kiwis must be no more than $6.
Therefore, we can write the inequality:
$2.55 + $0.50x ≤ $6
Simplifying this inequality, we get:
$0.50x ≤ $6 - $2.55
$0.50x ≤ $3.45
x ≤ $3.45 ÷ $0.50
x ≤ 6.9
Therefore, the possible values for the number of kiwis that Serena can buy is 0 ≤ x ≤ 6.9.