Got it. Thanks for the tip.
This
Solve[{a==2*c,a+2*b==3*c+d,a==2*d,b==c},{a,b,c}]
or even just this
{a==2*c, a+2*b==3*c+d, a==2*d, b==c}
WA link
appear to work.
Assignments to named variables, especially names of more than a single character, have been an issue in WA.
