Răspuns :
a - b = 900
a : b = 10
a = 10 × b
10 × b - b = 900
9 × b = 900
b = 900 : 9
b = 100
a - b = 900
a = 10 × b
a = 10 × 100
a = 1000
a - b = 900 ⇒ 1000 - 100 = 900
a - b = 900
a : b = 10
a = 10 × b
10 × b - b = 900
9 × b = 900
b = 900 : 9
b = 100
a = 10 × 100
a = 1000