In the seventh grade, the first unit of mathematics in the second volume of Zhejiang Education Edition always reviews the ninth and 10 questions in Group B.

(9) Draw a picture, with point D as the height on the side of AB and point AB as the point E..

So ∠ bed = ∠ c = 90.

And BD shares ∠ABC, so ∠CBD=∠EBD.

And because BD=BD.

So △CBD is equal to △EBD.

So CD=DE=3

That is, the distance from point D to AB is 3.

10) Let the perpendicular line of AB intersect with AB at point E and with AC at point D..

Therefore, AE = be, ∠ aed = ∠ bed = 90.

And DE=DE

So △ADE is equal to △BDE.

So AD=BD=7cm.

And AC= 10cm.

So CD= 10-7=3cm.

Judging from these two questions, you are not very skilled in proving the congruence of triangles.