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The chart shows you lines of equal declination $D$. You identify your location on the chart (which you have done and marked with an X in your second image). Then you determine on which line you are. It looks like the point is between the -26° line and the -28° line, so let's call it $D=-27^\circ$. That gives you a magnetic track of:  \varphi_\text{mag} = \...