Lisa earns a profit of $3 on each ribbon that she sells, and $5 on each bracelet. If at the end of the day Lisa has earned $120 and she has sold at least 10 pieces of each item. At least how many bracelets she has sold?
Choices
A) 2  B) 5  C) 9  D) 12  E) 15
Since Lisa has sold at least 10 pieces for each item, let us say Lisa sells (10 + r) number of ribbons and (10 + b) number of bracelets, her profit for the day = 3(10 + r) + 5(10 + b)   =&gt; 3(10 + r) + 5(10 + b) = 120   =&gt; 30 + 3r + 50 + 5b = 120   =&gt; 3r + 5b = 120 - 30 - 50= 
<gadget id="calculator">120 - 30 - 50</gadget>
<output>40</output>
40=&gt; 5b = 40 - 3r   =&gt; b = 8 - (3/5)r   To minimize b, we need to maximize r and it will be a multiple of 5.   r = 5, b = 8 - (3/5)5 = 5   r = 10, b = 8 - (3/5)10 = 2   Beyond that b will become -ve. So Lisa has sold at least 10 + 2= 
<gadget id="calculator">10 + 2</gadget>
<output>12</output>
12 bracelets.   Answer: 12
<result>D</result>
Lisa earns a profit of $3 on each ribbon that she sells, and $5 on each bracelet. If at the end of the day Lisa has earned $120 and she has sold at least 10 pieces of each item. At least how many bracelets she has sold?