Весь путь автомобиля примем за единицу (целое).
1) 1 - 5/12 = 12/12 - 5/12 = 7/12 - оставшаяся часть пути;
2) 15/28 · 7/12 = (5·1)/(4·4) = 5/16 - часть пути, пройденного за второй час;
3) 7/12 - 5/16 = 28/48 - 15/48 = 13/48 - часть пути, пройденного за третий час;
4) 5/12 - 13/48 = 20/48 - 13/48 = 7/48 - разница, равная 42 км;
5) 42 : 7/48 = 42 · 48/7 = 6 · 48 = 288 (км) - весь путь автомобиля.
ответ: 288 км.
Проверка:
1) 5/12 · 288 = 120 км - пройдено за 1-й час;
2) 15/28 · (288 - 120) = 90 км - пройдено за 2-й час;
3) 13/48 · 288 = 78 км - пройдено за 3-й час;
4) 120 - 78 = 42 км - на столько меньше пройдено за 3-й час.
I farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravy
2)15+23=38
3)38×2=64
4)15+23+64=102