In a right triangle, the sum of the right angle and an acute angle is 138°, what is the measure of the acute angle?
一个直角三角形中，直角与一个锐角的和是138°，求这个锐角的度数是多少？
<gadget id="calculator">138 - 90</gadget>
<output>48</output>

<result>48</result>