I am a relatively new user of maple. I am trying to solve an equation of the form
`y=(a*c)/(a+b)`

. I would like to solve for another variable x which is equal to `a/(a+b)`

. When
I use

algsubs(a/(a+b)=x, y);

I receive an error stating: Error, (in algsubs) cannot compute degree of a pattern in a.

I think algsubs cannot recognize a "buried" pattern. I tried to rewrite your eqation as:

` y:=a/(a+b)*c`

and then

`algsubs(a/(a+b)=x,y);`

But that failed to! I think what happens here is that when you enter your equation, maple stores it as

` y=a*c/(a+b)`

and cannot ﬁnd the unique "pattern" `a/(a+b)`

in that expression. This seems
to be a problem with algsubs. Perhaps someone else can ﬁnd a solution.

Note the expression `y=(a*c)/(a+b)`

cannot be handled by algsubs but the substitution
expression `a/(a+b)=x`

has not the appropriate form.

First you can change the substitution expression `a/(a+b)=x`

and then use algsubs or
subs:

eq_y := y = (a*c)/(a+b); a/(a+b)=x; isolate(%, (a+b)); algsubs(%, eq_y, b); subs(%%, eq_y); a c eq_y := y = ----- a + b a ----- = x a + b a + b = a/x y = c x y = c x

Second you use powsubs of the student package to substitute a factor:

student[powsubs](a/(a+b)=x, eq_y); y = c x