I go to school at 7:15.My sister goes to school at 7:15 too.

My sister and I both go to school at 7:15.
再问： Ivan lives on the tenth floor.Alice lives on the sixth floor合并为一句
再答： Ivan lives on the tenth floor and Alice lives on the sixth floor. 这里因为两个人住的不是同一层，所以中间加个and就可以了。 前面因为两个人都是7：15去学校，可以用both合并。 希望帮到你。