Answer:
again i didnt answer the question i just found someone who did
hope it helps :)
Step-by-step explanation:
Let +a+ = liters of pure acid needed
Let +b+ = liters of 10% solution needed
+.1b+ = liters of pure acid in 10% solution
-----------------------------------------
(1) +a+%2B+b+=+135+
(2) +%28+a+%2B.1b+%29+%2F+135+=+.2+
---------------------------
(2) +a+%2B+.1b+=+27+
(2) +10a+%2B+b+=+270+
------------------------
Subtract (1) from (2)
(2) +10a+%2B+b+=+270+
(1) +-a+-+b+=+-135+
----------------------
+9a+=+135+
+a+=+15+
and
(1) +a+%2B+b+=+135+
(1) +15+%2B+b+=+135+
(1) +b+=+120+
-------------------
15 liters of pure acid are needed
120 liters of 10% solution are needed
--------------
check:
(2) +%28+a+%2B.1b+%29+%2F+135+=+.2+
(2) +%28+15+%2B.1%2A120+%29+%2F+135+=+.2+
(2) +27%2F135+=+.2+
(2) +27+=+27+
