How does b-a =2

Question

It says

Var a = 4+2
Var b = 15-a
Var a = ( something ) / (b-a)

Answer 1

Var a = 4+2=6
Var b = 15-a=9
Var a = ( something ) / (b-a)=(S)/(9-6)=(S)/3=21/3=7 => b-a=9-7=2

right?

Answer 2

the first line 'a' is 6
the second line 'b' is 9
so the third line has 'a' and 'b' to be 6 & 9 respectively
b-a is supposed to be '3'
where did you get the '2' from?

Answer 3

I figured it out i was doing the division and i forgot / means division

Answer 4

Ok If you have any other question you can ask here

Answer 5

If you have
a=S/3
b-a=2=9-a
then you change operators from sides and you have
9-2=a=7

but If you want
Var a=(S)/(b-a)
Var a=(S)/(2) => b-a=2 ; 9-a=2; a=9-2=7