Answer: 25 ounces
Step-by-step explanation:
The equation would be 0.2∙25+0∙x=0.1(25+x) because 20% of boric acid would be = to 0.2. water doesn't have any acid in it so it would be 0. since annabel wants a 10% solution that would mean that the total about would be 0.1 of boric acid. The ounces she needs for the 0.2 boric acid solution is 25 while the other is unknown so that would be x. when you put them together it would be 25+x. then you just multiply the ounces and the acid together and you get 0.2∙25+0∙x=0.1(25+x). when you solve it it would be x=25.