From 4a + 7b - 12c subtract 8a - 9b + 12d.

-4a + 16b -12c -12d

Step-by-step explanation:

Given:  From 4a + 7b - 12c subtract 8a - 9b + 12d.

We are given two algebraic expression. We can add/subtract only the like terms.

(4a + 7b  -12c) - (8a -9b +12d)

Now we have distribute the negative sign inside the second expression (8a -9b +12b). If we do, the sign changes.

4a + 7b -12c -8a + 9b -12d                                          [Sign rule: -(-) = +; -(+) = -]

Now we can combine the like terms

= (4a - 8a) +(7b + 9b) -12c -12d

= -4a + 16b -12c -12d

answer:

the position of equilibrium will shift to the left.

step-by-step explanation:

the general equation for the dissociation of a weak base is

b + h₂o   ⇌   bh⁺ + oh⁻

according to le châtelier's principle, when a stress is applied to a system at equilibrium, the system will respond in a way that tends to relieve the stress.

if you apply a stress by adding more bh⁺ or oh⁻,   the system will respond by moving in a direction that gets rid of the added ions.

the position of equilibrium will shift to the left, forming more of the undissociated base.