The quotient rule is as follows
((l)•(h’) - (l’)•(h))/(l)^2
With l representing “low” or “bottom equation” and h representing “high” or “top equation”
Let’s plug in v^k and v^h in this case
((v^h)(v^k)’ - (v^h)’(v^k))/(v^h)^2
Simplify 2.8y + 6 + 0.2y to 3y + 6
subtract 3y from both sides
simplify 5y - 15 - 3y to 2y - 15
add 15 to both sides
simplify 6 + 15 to 21
divide both sides by 2
switch sides
Answer: y = 21/2
*in decimal form this would be 10.5
Now, the percentage figures of say, 70%, 95% and so on, we'll use the decimal format of the, thus 70% is just 70/100 or 0.7 and 95% is just 95/100 or 0.95 and so on
so

whatever "x" and "y" amounts are, we know, they must add up to 160 pints
thus x + y = 160
now, whatever the concentrated amount of solute in the mixture, we know they must add up to 160*0.85 or 136
thus 0.7x + 0.95y = 136
thus

solve for "x", to see how much of the 70% pure juice will be needed
what about "y"? well, y = 160 - x
The answer is 1.2
You just look at the graph at x = 6.
The point is marked as (-6, 1.2).