Question

Brown rocks cost $5 per pound. Beige rocks cost $11 per pound. How many brown rocks are needed to create a 10 lb mixture that costs $6.80 per pound? PLEASE

Answer 1

put x = pounds of brown rocks and so 10-x is pounds of beige rocks.
then your total cost of brown rocks is 5x and cost of beige rocks is 11(10-x) for a total of
\[5x+11(10-x)\] and you want this to equal 6.8 times 10 or 68 so solve
\[5x+11(10-x)=68\] for x

Answer 2

i get x = 7