PART A: The answer is: x = 0.6x + 1
Let x be the total number of liquid in the bottle. l stands for lemon juice, and w stands for the water.
So, x = l + w
We know that in the bottle there is 1 liter of water, thus:
w = 1L
Further, lemon juice is 60% of the total liquid.
l = 60% · x = 60/100 · x = 0.6x
Now, let's just change this in the equation:
x = l + w
x = 0.6x +1
PART B: The answer is 1.5 L.
Let's use the equation from the part A to calculate the total amount of liquid:
x = 0.6x + 1
x - 0.6x = 1
0.4x = 1
⇒ x = 1 ÷ 0.4 = 2.5 L
Since l = 0.6x, then:
l = 0.6 · 2.5 = 1.5 L
Let's just check the answer:
x = l + w
2.5 L = 1.5 L + 1 L
2.5 L = 2.5 L