how to convert if condition into problem based approach in optimization problem

I have the problem below and I need to convert to problem based approach optimization problembecause I can not use if condition in this type of optimization problem.

if M <= z && K<=90%

x= z - u

end

if z <= M <= y && K >=90%

x=0

end

if M<= y && K<=25%

x= u - y

end

[Aditya Patil]

You may be able to consider these as separate variables(eg: x1, x2,x3), but the exact form will depend upon what other constraints are present, and what your optimization function is.