The Literary Lion Book Store has a coffee bar that sells its own blend of coffee. Each morning the manager mixes up 120 pounds of the special blend to sell to his customers. The coffee is a mixture of Columbian coffee selling for $5.00 per pound and Brazilian coffee selling for $8.00 per pound. The mixture sells for $7.00 per pound. How many pounds of Brazilian coffee is in the 120 pound mixture?

Question

anonymous · Answer

if you call the amount of brazillian coffee $x$ then the amount of columbian coffee is $120-x$ ( since they add up to 120)
cost is 
$$8x+5(120-x)$$which should total $7\times 120$ so set 
$$8x+5(120-x)=840$$ and solve for $x$

anonymous · Answer

tbh this problem still confuses me.