please answer this with full explanation
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Step-by-step explanation:
a21=?
a12=92
a16=122
an=a+(n-1)d
a12=a+11d
a+11d=92. (1)
a+15d=122. (2)
subtract equation (1 ) from (2)
4d=30
d=30/4
d=15/2
put value of d in equation (1)
a+11(15/2)=92
a+165/2=92
a=92-165/2
a=(184-165)/2
a=19/2
a21=a+(n-1)d
a21=(19/2)+(20)(15/2)
a21=(19/2)+150
a21=(19+300)/2
a21=319/2
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