tlng jwb kah!!pakai crnya!!

7x+5x=180°
12x=180°
x=180:12
x=15°
➡7x=7×x
=7×15 =105°
➡5x=5×x
=5×15 =75°
➡3x+17 = 3(15)+17
=45+17 = 62°
<QRS = 180°-62°
=118°