Asolution of ammonia nh3(aq) is at equilibrium. how would the equilibrium
change if nh4+ were removed from the solution?

If NH4+ is removed,  the reaction will shift toward products to replace the product removed.  This means the reaction will shift to the right.

Explanation:

A solution of ammonia NH3(aq) can be written through the following equation:

NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH⁻(aq)

If the concentration of one of the reactants changes, the balance will shift in such a way that the change in concentration is counteracted.

If NH4+ is removed, now there is less product, so the reaction will shift toward products to replace the product removed.  This means the reaction will shift to the right.

This principle is due to the fact that the equilibrium constant for this reaction is constant at a certain temperature. The ratio of reactants and products is fixed. Any change in concentration disrupts the balance and will result in the balance being restored.