Let A be set of first ten natural numbers and R be a relation on A, defined by $(x,y)\in R\Rightarrow x+2y=10,$ then domain of R is

Given that $A$ be the set of all first ten natual numbers

$A=\left\{1,2,3,4,...,10\right\}$

The given relation is $x+2y=10$

Possible ordered pairs are $\left(2,4\right),\left(4,3\right),\left(6,2\right),\left(8,1\right)$

Hence, $R=\left\{\left(2,4\right),\left(4,3\right),\left(6,2\right),\left(8,1\right)\right\}$

Therefore, the domain of the relation is $D=\boxed{\left\{2,4,6,8\right\}}$