Ruel has four books of 10 stamps and six books of 15 stamps. How many stamps does Ruel have?
Ruel has a total of 4 x 10 = 
<gadget id="calculator">4*10</gadget>
<output>40</output>
40 stamps from the four books.
He also has 6 x 15 = 
<gadget id="calculator">6*15</gadget>
<output>90</output>
90 stamps from the six books.
Therefore, he has a total of 40 + 90 = 
<gadget id="calculator">40+90</gadget>
<output>130</output>
130 stamps.

<result>130</result>