7) $6 \mathrm{lbs}$. of mixed nuts containing $28 \%$ peanuts were mixed with $12 \mathrm{lbs}$. of another kind of mixed nuts that contain $22 \%$ peanuts. What percent of the new mixture is peanuts?

Step 1 ：First, we calculate the total amount of peanuts in each mixture. In the first mixture, there are $6 \times 0.28 = 1.68$ pounds of peanuts. In the second mixture, there are $12 \times 0.22 = 2.64$ pounds of peanuts.

Step 2 ：Next, we add the total amount of peanuts together to get the total amount of peanuts in the new mixture. So, $1.68 + 2.64 = 4.32$ pounds of peanuts.

Step 3 ：Then, we add the total weight of the two mixtures to get the total weight of the new mixture. So, $6 + 12 = 18$ pounds.

Step 4 ：Finally, we calculate the percentage of peanuts in the new mixture. The percentage is equal to the total weight of peanuts divided by the total weight of the mixture, multiplied by 100. So, the percentage of peanuts is $\frac{4.32}{18} \times 100 = \boxed{24\%}$.