Question

13 subtracted from a number w is 15.

Answer 1

W-13=15|+13
w=15+13
x=28

Answer: w=28

Answer 2

W is 15 when 13 has been subtracted from it? So, you need to add back what was subtracted giving you 28. I think that's what you were asking, you weren't all too clear. Hope I helped.