The angle abc is equal to 75 degrees, and ab is equal to ac.
The angle abc is greater than 75 degrees and the angle acd is greater than 45 degrees, that is, the angle acd is greater than the angle cad and the ad is greater than the cd. Take a point B on am to make ab equal to ab and cd equal to B, that is, ad is greater than B, and ab +b and C are greater than ac, that is, ab +ad is greater than ac. In the above three cases, ab is greater than ac-cd.
I think the answers on your test questions are very detailed, and your basic skills should be better, so I probably talked about my ideas and sorted them out myself.