Can you please help me ​

Use Pythagorean theorem

a² + b² = c²

30² + b² = 78²

b² = 5184

b = √5184

b = 72

I think its 72

Step-by-step explanation:

Im not 100% but i think you have to add every side and you have to comlite 180 so 180-78-30=72

Im sure that this is what you do with the corners but it could be the same for the sides maybe

i hope this is what you were looking for.

see attached graph