I don’t understand how to do this.

Answer:
46degrees
Step-by-step explanation:
From the question, we are told that both triangles are similar, hence;
<E = <S
<D = <R
<F = <T
From triangle DEF
<D + <F + <E = 180
Since <D = <F = 67
67 + 67 + <E = 180
134 + <E = 180
<E = 180 - 134
<E = 46degrees
Since <E = <S, hence the measure of <S is 46degrees