Answer:
4
Explanation:
The problem statement tells you the constant of proportionality is y/x. The graph shows y=4 for x=1. Then y/x = 4/1 = 4.
The constant of proportionality is 4.
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Caveat
Before you copy this answer, be certain the graph in your problem statement is identical to this graph. If your marked point has different coordinates than (1, 4), your constant of proportionality may be different. It will still be computed as y/x, but you need to use the x and y values of the marked point on your graph (or those of any other point whose coordinates you can read).