Blending spice:

Spice of life sells ground sumac for $1.35per ounce and ground thyme for $1.85 per ounce. Aman wants to make a 20 oz Zahtar seasoning blend using the two spices that sells for $1.65 per ounce. How much of each spice should Aman use?

I know that there are 28 grams in a pound i am lost when it comes to this problem
Please help!

2 answers

1.35 s + 1.85 t = 1.65 * 20

s + t = 20 so s = (20-t)

===========================
1.35 (20-t) + 1.85 t = 33

solve for t, go back and get s
Sumac: 21.9 oz
Thyme: 1.9 oz