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Because of a linear pair then because of vertical angles and because all angles have to be 180 added up
Answer:

Step-by-step explanation:
![\dfrac 12 \left[\sin(a+b)+\sin(a-b) \right]\\\\\\=\dfrac 12\left[ 2 \sin a \cos b\right]\\\\\\=\sin a \cos b](https://tex.z-dn.net/?f=%5Cdfrac%2012%20%5Cleft%5B%5Csin%28a%2Bb%29%2B%5Csin%28a-b%29%20%5Cright%5D%5C%5C%5C%5C%5C%5C%3D%5Cdfrac%2012%5Cleft%5B%202%20%5Csin%20a%20%5Ccos%20b%5Cright%5D%5C%5C%5C%5C%5C%5C%3D%5Csin%20a%20%5Ccos%20b)
Answer:
Step-by-step explanation:
3 times 60 = 180 minutes
10 * 60 = 600 minutes
600/20 = 30 * 3 = 90 hours
Answer:
12
Step-by-step explanation:
4x + 5y = 3 ................ (i)
kx + 15y = 9................(ii)
Dividing eqn (ii) by 3, we get,
k/3 x + 5y = 3.............(iii)
Subtracting eqn (iii) by eqn (i), we get,
-4x - k/3 x = 0
or, -(4 - k/3 )x = 0
or, 4 - k/3 = 0/x
or, 4 - k/3 = 0
or, 4 = k/3
or, k = 4*3
:. k = 12 (Ans)