The resulting solution would have 40% acid because the volume would double, but the amount of acid would add. find the average acidity of the solution and thats your aanswer
The slope, if increased, would make the line y=2x-7 steeper. If you were to increase the y intercept, you would just move the line, not tilt it. Suggest changing it to 4x-7 = y or 8x-7= y, if you increase the slope, it'll make it steeper.
