Sorry this is a really stupid question.

Ive been going back to basics and im a bit lost (probably tired so I cant see the obvious)

so im working out 87v+38w=d

ive done the basics pretty well and have d=1.

Now backwards substitution is spinning my head a bit.

11=87-2*38
5=38-3*11
1=11-2*5

So using backwards substitution I have:

1=11-2(38-3*11)
1=7*11-2*38

This is where im a bit unsure about the order so we have reduced the equation down and im not entirely sure I understand intuitively where the 7 came from.

have we (11-(-3))/2=7

Again sorry this is such a basic question but I want to be sure I understand what is happening explicitly.