The total number of students who studied only two subjects is 13.
The given parameters:
The number of students who studied only two subjects can be determined by applying overlapping three sets formula as shown below;
[tex]Total = n(phy) + n(geo) + n(econ) + n(none)- n(double) - 2(all \ subjects)\\\\55 = 21 + 24 + 23 + 2x-n(double) - 2(x)\\\\55 = 68- n(double)\\\\n(double) = 68-55\\\\n(double) = 13[/tex]
Thus, the total number of students who studied only two subjects is 13.
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