3a-28-7a=10a I don’t understand it

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 %

The slope of the line passing through the points (2, 7) and (-4, 8) is

In a rational number twice the numerator is 2 more than the denominator. if 3 is added to each, numerator and the denominator, the new fraction is 2/3. find the original number