How to have Maple Flow solve 5*a^2 + 2*b - 7 = 0 when a:=1?

I enter ...

5*a^2 + 2*b - 7 = 0

a:=1

b=

and get b=b not b=1

I thought I figgured out how to do this a couple of weeks ago but after an absense from Maple Flow I'll be darn'd if I can remember how to make it work.

Of course I can manually manulape the the equation...

b := (-5*a^2 + 7)/2

a:=1

then enter b =

and get the rusults 1 ... but I thought Maple Flow would do all that for me in the first instane above...

Thanks for any help.