Could it be an Imaginary number?
Step 1 (simplify):
3+5x(2-1)
8 x 1
Step 2 (solve):
8 x 1 = 8
8 is your answer. Hope this helps :)
4 days 10 days Cross Multiplication
---------- = ------------
7 mins x
4x = 7*10
4x = 70
x = 70/4
x = 17.5
17.5 minutes = x
Since 25% is smack in the middle between 20% and 30%, it will take equal volumes of ech to make a 25% solution.
Since 4 gallons of 30% solution was used, so 4 gallons of 20% solution will be needed.