Set Notation Excercise I am working through some set theory exercises, and am stuck with this one:
$A = \left \{ 2,4,6,7,11 \right \}$
Find the set S1:
$S1 = \left \{ (n+4): n \in A) \right \}$
Taking away 4 from each member, of the set I get:
$A = \left \{ -2,0,2,3,7 \right \}$
The applet tells me the answer is wrong, but I can't figure out how!

I think you don't want to take away $4$ but you want to add $4$:
$$ S_1 = \{ n + 4 \mid n \in \{ 2,4,6,7,11\} \} = \{ 2 + 4, 4 + 4, 6 + 4, 7 + 4, 11 + 4\} = \{ 6, 8, 10, 11, 15\}$$
