13) a merchant has coffee worth $60 a pound that she wishes to mix with 90 pounds of coffee worth
$90 a pound to get a mixture that can be sold for $70 a pound. how many pounds of the $60 coffee
should be used?
a) 270 pounds
b) 180 pounds
c) 90 pounds
d) 135 pounds

B) 180 pounds

Step-by-step explanation:

if the mixture is in the ratio 1:1 the new mixture would cost $75

but we want a price of $ 70 so the ratio should be 2:1 that is 2 units of 60 $ coffee and 1 unit of 90$ coffee. this would give 70$  cost price .

correct answer:

b.(19,-2)