4 per 5 ( x + 1 ) =20

4/5 (x + 1) = 20
4/5x + 4/5 =20
4/5x =20 - 4/5
4/5x = 100/5 - 4/5
4/5x = 96/5
x = 96/5 x 5/4
x = 24
Maaf kalau salah