convert 6A base 16 into base 10.
(6)(161)+(10)(160)=96+10=106(6)(161)+(10)(160)=96+10=106
Then, let’s convert 211 base x into base 10, result must equal to 106.
(2)(x2)+(1)(x1)+(1)(x0)=106(2)(x2)+(1)(x1)+(1)(x0)=106
2x2+x–105=02x2+x–105=0
Factoring the equation and exclude the non-integer result, we will get x=7x=7
it’s base 7.