Answer: The measure of angle A is 60 degree.
Step-by-step explanation:
It is given that the Triangles A B E and D C E share vertex E. Angle B is 18 degrees. Angle C is 43 degrees. Angle D is 35 degrees.
According to angle sum property, the sum of angles of a triangle is always 180 degree.
In triangle CDE,
![\angle ECD+\angle CDE+\angle DEC=180^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/ffe98h9axw2rivopcu1b6vcxd9so93wlk2.png)
![43^(\circ)+35^(\circ)+\angle DEC=180^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/rvsrvm21apc5uj2fqvy64qf85dd3h1pmyv.png)
![78^(\circ)+\angle DEC=180^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/udut8jccu0azseecf1b4fe6ymavbvog4fv.png)
![\angle DEC=180^(\circ)-78^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/swmnimwxr77bmsmv95yozbjzzir9b024wl.png)
![\angle DEC=102^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/kd9y9fuel8g41i9knxuun5kovu7yk6g8mw.png)
According to opposite vertical angle property.
![\angle AEB=\angle DEC](https://img.qammunity.org/2019/formulas/mathematics/high-school/x5nvz53ml4hw8vf1z9fe840mbqhf9qjb9a.png)
![\angle AEB=102^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/s6dwanbif093duqlbd06u4hxkjasasq1ew.png)
Use angle sum property is triangle ABE.
![\angle ABE+\angle BEA+\angle EAB=180^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/3ervgvo5ruuajen02e6e4v8eymzh58zi2j.png)
![\angle ABE+102^(\circ)+18^(\circ)=180^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/lffpianhabwls6ihe64q47y62l9966ybox.png)
![\angle ABE+120^(\circ)=180^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/8dnty1hudf2un8kg2kgabvzbxtfsdtijh6.png)
![\angle ABE=60^(\circ)](https://img.qammunity.org/2019/formulas/mathematics/high-school/by62aunklv5kb12cyffzlv6393obdua75d.png)
Therefore, the measure of angle A is 60 degree.