3(7-2r)=21r-6 how to solve step by step

Write the system of equations represented by the matrix. 0 1 2 4 -2 3 6 9 1 0 1 3

The edge of a cube was found to be 30 cm with a possible error in measurement of 0.4 cm. use differentials to estimate the maximum possible error, relative error, and percentage error in computing the volume of the cube and the surface area of the cube. (round your answers to four decimal places.) (a) the volume of the cube maximum possible error cm3 relative error percentage error % (b) the surface area of the cube maximum possible error cm2 relative error percentage error %

Need same math paper but the back now i hope your able to read it cleary i need with hw