Răspuns :
7/10 × x +12 = x
x - 7x/10 = 12
(10x - 7x) / 10 = 12
3x/10 = 12
x = (12×10)/3
x = 40 km
x - 7x/10 = 12
(10x - 7x) / 10 = 12
3x/10 = 12
x = (12×10)/3
x = 40 km