Question

The domain of the following relation: R: {(3, 5), (8, 6), (2, 1), (8, 6)} is No domain exists {1, 5, 6} {3, 8, 2, 8} {2, 3, 8}

Answer 1

The domain is the inputs or x values
(x,y)
x is the domain

for (3,5), (8,6), (2,1) and (8,6)
list all x and ignore repeats

3,8,2
list in order

2,3,8

answer is {2,3,8}

Answer 2

Ahemmm the domain for a x,y pair set is always the "x" value, or the 1st value in the pair, thus   $\bf \{(\boxed{3}, 5), (\boxed{8}, 6), (\boxed{2}, 1), (\boxed{8}, 6)\} \impliedby \textit{that's the \boxed{domain}}$

of course, the 8 is there twice, so, you don't need to put it twice, just once.