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Assume the base of the number is $x$.
Therefore, $=> (4)x+(2)x=(11)x$ $=> 4x^0+2x^0=1x^1+1x^0$ $=> 4+2=x+1$ $=> 6=x+1$ $=> x=6-1$ $=>x=5$
Hence base should be 5 for the given expression.
Let the base be x
= $(4)_{x} + (2)_{x} = (11)_{x}$
= $4 + 2 = x + 1$
= $x = 6-1 = 5$
Correct answer: 5