Does anyone know the answer to this ?

Which coefficient matrix represents a system of linear equations that has a unique solution ? options in photo*

Find the perimeter of the triangle with vertices  d(3, 4),  e(8, 7), and  f(5, 9). do not round before calculating the perimeter. after calculating the perimeter, round your answer to the nearest tenth.  

Me! i will mark you brainliest if you are right and show your i don't get polynomials and all the other stuff. multiply and simplify.2x(^2)y(^3)z(^2) · 4xy(^4)x(^2)show your