Determining what relation means

Question

If we have to consider the relation R from {1,2,3,4} to {3,4,6,7,9} given by aRb ↔ b = a + 3 then would the relation given be {1,2,3,4,6,7,9}? I'm a little confused on what is meant when I'm being told to consider a relation R from one relation to another.

Answer 1

A relation on sets $A$ and $B$, $a R b$, $a \in A, b \in B$ is a subset of $A \times B.$ If $a R b,$ then $(a,b) \in R.$ So if $b=a+3,$ then $(a,b) \in R.$

$$R= \{ (1,4), (3,6), (4,7)\}.$$