Question 1013544
<br>
Here is a solution using a non-traditional method that can be used to solve any 2-part mixture problem like this.  This method can be especially fast and easy if the numbers in the problem are "nice" (which in this problem they are not....)<br>
(1) Use a number line if it helps to observe/calculate that 60% is 35/45 = 7/9 of the way from 25% to 70%.
(2) That means 7/9 of the mixture must be the 70% acid solution which is being added.<br>
7/9 of 100g is 700/9 grams.<br>
ANSWER: 700/9 grams<br>