Answer: 
Step-by-step explanation:
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Answer-
Dont ask me why...I cant really explain it...but if u have 1 repeating decimal, u put it over 9. If u have 2 repeating decimals, u put it over 99....3 repeating decimals, put it over 999.
Examples :
0.7 (repeating) = 7/9
0.27 (repeating) = 27/99 when simplified = 3/11 <===
0.444 (repeating = 444/999
I would say that there are 29 boys in the class.
(a-b) X (a+b)
= aXa - bXa +aXb -bXb (distributing)
Now, cross product of a vector with itself = 0
so, aXa = 0, bXb = 0
Also, aXb = - bXa
so,
(a-b) X (a+b) = 0 + aXb + aXb + 0
= 2aXb
hence, proved :)
