(20x−28y)−(21x−28y)=108−112

Sure, let's solve the equation step by step.

First, let's simplify the equation by combining like terms:

(20x - 28y) - (21x - 28y) = 108 - 112

This simplifies to:

-1x = -4

Then, to solve for x, divide both sides by -1:

x = 4

So, the solution to the equation is x = 4.