a and b represent the slopes in the equations. Use the y-mx+b formula to realize this. M is the slope, a or b in this question. The lines both have positive slopes so B or C cannot be the answer. I cant see the image properly, but if the y int is at 0 then A is the answer, but if it is above 0 then D will be your answer.
one year as a full-time student........ hope this helps you
0.12 L will be grape juice
0.88 L will be water
for 100% (the full amount) - 12 % (grape juice amount) = 88 % (water)
hope this helps