Answer
$m\angle{A} = 72^o$
Work Step by Step
The sum of the three interior angles of a triangle is 180 degrees.
Thus,
$60^o + 48^o + m\angle{A} = 180^o
\\108^o + m\angle{A} = 180^o
\\m\angle{A} = 180^o - 108^o
\\m\angle{A} = 72^o$
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