D) Seven years ago, father was seven times as old as his son was. Three years hence, he will be three times as old as his son. Find their present age.​

Type the correct answer in the box. consider the system of linear equations below. rewrite one of the two equations above in the form ax + by = c, where a, b, and c are constants, so that the sum of the new equation and the unchanged equation from the original system results in an equation in one variable.