Its because its: 2+5×(8−5)

No it isn't. It's 2+5(8−5). Different expression, but in this case co-incidentally the same answer. Preface the first 5 with a Division and you get different answers.

My calculator app

Was written by a programmer who didn't check the rules of Maths first. The only e-calc I've ever seen give the correct answer is MathGPT

not writing it properly

Except it is written properly, as per Maths textbooks