Сделайте, перефразируйте, употребив пассивную форму сказуемого (исполнителя действия можно не указывать, если в этом нет необходимости). 1) tractors can casily drive along rough ground. 2)they have measured the angles of the triangle. 3)they promised the workers better conditions. 4)you need the greater effort to lift the weight. 5)by that time we had already changed our plans.
2)The angles of the triangle have been measured
3) The workers have been promised better conditions.
4) The greater effort is needed to lift the weight.
5) Our plans had been already changed by that time