Как перевести на английский: "При решении данной проблемы будем считать коэффициент "a" равным нулю. "

In solving this problem, we assume that the coefficient "a" zero
грамматически правильный перевод.

in solving this problem, we will assume the coefficient "a" equals zero.

(Re)solving/Fixing this problem, we consider the coefficient "a" as being equal to zero (или ...we consider that the coefficient "a" is equal to zero).

At the solution of this problem we will consider factor of "a" equal to zero.

To solve this problem, let's assume that the coefficient of "a" is zero.