50:[ (4·5) - (36:2) ]=y

What is the value of y?

Y=25 ...

Isn't it 25? Order of Operations says P. E. D. M. A. S ... Parenthesis, Exponents, Division, Multiplication, Addition, and Subtraction.

Remove 50 and y from the equation for now.

[ (4·5) - (36:2) ]

Solve what is in the parenthesis first: 4*5 = (20) 36/2 = (18)

Now you should have [ (20) - (18) ].

[ (20) - (18) ] = 2

Now you can add 50 back to the back to the beginning of the equation.

50: [ (20) - (18) ]

50 : 2

25

If this is incorrect I sincerely apologize!