Probably best to start with
You can get 4 simultaneous equations by multiplying out the matrices. And a 5th equation .
Your simultaneous equations will be quadratic so when finding solutions you will get square roots of numbers, you can find more inequalities by ensuring that the square roots are the square root of a positive number.
You might also be able to get equations by knowing that all elements are natural numbers. For example, if you found that since p+r must be a natural number d must be a multiple of b+c, so you can say that d=k(b+c)