Achemist has 300 grams of 20% hydrochloric acid solution. he wishes to drain some and replace it with an 80% solution so as to obtain a 25% solution. how many grams must he drain and replace with the 80% solution?

You’re ordering more thread for blue jeans co. you usually purchase from ted’s threads, which sells 12 thread spools for $27. you recently received a notice from wade's wares that says you can buy thread from them for $2.30 each for the first 2 dozen and $2 a spool thereafter. you need to order 5 dozen spools. what percentage can you save by going with wade’s wares?