Whats the answer? the pic is attached

Find the nonpermissible replacement for binthis expression.b2/5b +5

Arefrigeration system at your company uses temperature sensors fixed to read celsius (°c) values, but the system operators in your control room understand only the fahrenheit scale. you have been asked to make a fahrenheit (°f) label for the high temperature alarm, which is set to ring whenever the system temperature rises above –10°c. what fahrenheit value should you write on the label?

Which best explains why this triangle is or is not a right triangle ?