The average of 13 numbers is 58. Average of the first 7 of them is 57 and that of the last 7 is 61. Find the 8th number?  Choose the correct choice from the following answers:
A) 72	B) 83	C) 45	D) 53	E) 64
Sum of all the 13 numbers = 13 * 58= 
<gadget id="calculator">13 * 58</gadget>
<output>754</output>
754   Sum of the first 7 of them= 7 * 57= 
<gadget id="calculator">7 * 57</gadget>
<output>399</output>
399   Sum of the last 7 of them= 7 * 61= 
<gadget id="calculator">7 * 61</gadget>
<output>427</output>
427   So, the 8th number= 427 + 399 - 754= 
<gadget id="calculator">427 + 399 - 754</gadget>
<output>72</output>
72.   72nswer:72
<result>A</result>
The average of 13 numbers is 58. Average of the first 7 of them is 57 and that of the last 7 is 61. Find the 8th number?