89 would be the correct answer
Yes that is true if you think of it as a point and the lines extending in both directions.
10lb. of jam needs 5lb. apple, or 2lb. of jam needs 1lb. apple.
Now we want 8lb. of jam.
Set up a proportion:
2/1=8/x
Solve for x by cross-multiplying.
2x=8
x=4 lb. of apple
