解:解方程,此方程的解为x = 100
x + 20 = x ÷ 5 + 100
x + 20 = x × 1/5 + 100
x + 20 = ( 1/5)x + 100
x - (1/5)x = 100 - 20
(5/5)x - ( 1/5)x = 80
(4/5)x = 80
x = 80 ÷ 4/5
x = 80 × 5/4
∴x = 100
答:此方程的解为x = 100