Question 1028648
{{{f(a,b) = 2a - 3b^2 + 7}}} ==> {{{f(b,3) = 2b - 3*3^2 + 7 = 90}}}

==> 2b - 27 + 7 = 90 ==> 2b - 20 = 90 ==>  2b = 110 ==> b = 55.