tolong dibantu kak no 19- 22 dengan caranya kak

20.
k Lngkrn = πd
125,6=3,14d
d=125,6:3,14
d=40


21.
2y=56°
y=28°

4x=56°
x=14°

x+y=28+14=42



22.
2x+3x+20°=180°
5x=180°-20°
5x=160°
x=32°

besar sudut c
3x
=3.32°
=96°

19. Diket : trapesium ABCD
                  AB//DC , AB = 8 cm
                   t = 7 cm
                 luas trapesium = 49 cm²
      ditanya panjang DC =...?
      jawab
        luas trapesium = (AB + DC) x t / 2
                           49 = (8 + DC) x 7 / 2
                     49 x 2 =  56 + 7DC
                          98  = 56 + 7DC
                       -7DC = 56 - 98
                        -7DC = -42
                            DC = -42/-7
                            DC = 6   ................(B)

20. diket keliling lingkaran = 125,6 cm
                  π = 3,14
       ditanya  diameter=...?
      jawab
          keliling lingkaran = πd
                        125,6     = 3,14. d
                                  d = 125,6 / 3,14
                                  d = 40  .....................(D)
      jawab