Sarah signed 1/2 of the Christmas cards, and Richard signed 3/8 of them. If there are 32 cards in
all, how many are left to be signed?
Options:  A) 6  B) 7  C) 4  D) 9  E) 2
1/2 x 32 = 16 Sarah signed   3/8 x 32 = 12 Richard signed   16 + 12= 
<gadget id="calculator">16 + 12</gadget>
<output>28</output>
28 are signed     32 - 28= 
<gadget id="calculator">  32 - 28</gadget>
<output>4</output>
4 cards left to be signed   correct answer 4
<result>C</result>
Sarah signed 1/2 of the Christmas cards, and Richard signed 3/8 of them. If there are 32 cards in
all, how many are left to be signed?