<PRE><B>Question 1097895</B>
Let
 B = number of type B lights
—

Compute value of lights:  $40*(number type A) + $50*(number type B) = $2580
and number of type A is 60-B:
 40(60-B) + 50B = 2580
  2400 - 40B + 50B = 2580
   10B = 180
{{{ highlight(  B = 18 ) }}}

—
Check:  
    40(60-B)+50B = 40(42) + 50(18) = 1680 + 900 = 2580
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