What is the solution of @[-2x + 5] <60

Answer 1

not familiar with @ as a mathematical operator

Answer 2

As written (losing the @)
[-2x+5] < 60
-2x+5 < 60
-2x < 55
x > -55/2

But you may have meant
|-2x+5| < 60
|2x-5| < 60
Now you have two parts:
2x-5 < 60
2x < 65
x < 65/2
------------
-(2x-5) < 60
2x > -55
x > -55/2
===============
so, -55/2 < x < 65/2