Respuesta :

I think it might be 12 but I'm sorry if its wronnngggg.
m<SRT = 180 - m<SRJ 
m<SRT = 180 - 140
m<SRT =  40


m<SRT + m<STR + m<RST = 180
40 + 8x +4 + 3x + 4 = 180
11x + 48 = 180
11x = 132
x = 12

m<S = 3x + 4
m<S = 3(12) + 4
m<S = 36 + 4
m<S = 40

answer
m<S = 40