a × ( b + 2 ) = 400 si a = 300 : b
Din relatia: a = 300 : b observam ca: a × b = 300
300 : b = a ⇒ 300 = a × b
a × ( b + 2 ) = 400
a × b + 2 × a = 400
300 + 2 × a = 400
2 × a = 400 - 300
2 × a = 100
a = 100 : 2
a = 50
a × b = 300
50 × b = 300
b = 300 : 50
b = 6