What is w--5 equals 4?

Answer 1

if w - - 5 = 4, then w+4 = 4, subtract 4 from both sides = w = 4 - 4, so w = 0

and now the correct answer

if w - - 5 = 4, then w+5 = 4, subtract 5 from both sides gives w = 4 - 5,

so w = -1