The best first step to solve the equation \( ax - 7 = 26 \) is to add 7 to both sides of the equation.
This will help isolate the term with \( x \) on one side, leading to:
\[ ax - 7 + 7 = 26 + 7 \]
which simplifies to:
\[ ax = 33 \]
After this step, you can proceed to solve for \( x \).