A small pizza has 6 slices, a medium pizza has 8 slices whereas a large pizza has 12 slices. How many slices of pizza will you have if you bought a total of 15 pizzas and you know you ordered 4 small pizzas and 5 medium pizzas?
We know that 4 small pizzas and 5 medium pizzas = 4+5 = 9 non-large pizzas were purchased.
Because a total of 15 pizzas were purchased then 15 - 9 = 
<gadget id="calculator">15-9</gadget>
<output>6</output>
6 large pizzas were ordered.
If 1 small pizza has 6 slices then 4 small pizzas will have 4 * 6 = 
<gadget id="calculator">4*6</gadget>
<output>24</output>
24 slices.
Similarly, If 1 medium pizza has 8 slices then 5 medium pizzas will have 5 * 8 = 
<gadget id="calculator">8*5</gadget>
<output>40</output>
40 slices.
Similarly, If 1 large pizza has 12 slices then 6 large pizzas will have 6 * 12 = 
<gadget id="calculator">6*12</gadget>
<output>72</output>
72 slices.
That means in total we have 24 small slices + 40 medium slices + 72 large slices = 24 + 40 + 72 = 
<gadget id="calculator">24+40+72</gadget>
<output>136</output>
136 slices of pizza.

<result>136</result>