Solve algebraically 6a + b = 16 and 5a - 2b = 19

This is a simultanious equation. As there are two unknown variables, it is impossible to find both a and b just using one of the equations. To make it possible to work out the unknowns, we need to have just one unknown. If we multiplied the first equation by 2, we will have 12a + 2b = 32. This then means if we added both equations together the (+2b) and the (-2b) will cancel each other out and we will be left with (12a + 5a) = (32+19). 17a = 51, so a = 3. We then put a back into one of the original equations to work out b. So 6 x (3) + b = 16. So b = -2.