The question is incomplete, the complete question is;
A grocer has 18 kg of black tea worth $3.5 per kg. She wants to mix it with green tea worth $2.6 per kg to sell the mixture at $2.9 per kg. How much of green tea should she use?
Answer:
36
Explanation:
Let the weight of the green tea used be x kg.
From the question:
We have:
18 kg of black tea at $ 3.5 per kg. Thus total cost of black tea is 18 x 3.5 = $ 63
Cost of green tea is $2.6 per kg. Total cost of green tea is 2.6 * x = $2.6x
Total weight of the mixture is 18 + x kg.
Total cost of the mixture is = $2.9 (18 + x)
Thus,
Total cost of black tea + total cost of green tea = Total cost of the mixture
$63 + $2.6 x = $2.9 (18 + x)
$63 + $2.6x = $52.2 + $2.9x
63 – 52.2 = 0.3 x
10.8 = 0.3 x
x = 10.8/0.3
x = 36
36 kg of green tea is needed