Form the pair of linear equations in the following problems and find their solution by substitution method : A’s present age is to B’s present age is 7 : 9. Twelve years ago, their ages were in the ratio 3:5. When would the ratio of their ages be 6 : 7 ?

Form the pair of linear equations in the following problems and find their solution by substitution method : A horse and 2 cows together cost ? 680. If a horse costs ? 80 more than a cow, find the cost of each.

Form the pair of linear equations in the following problems and find their solution by substitution method : Five years ago, I was thrice as old as my son and ten years later I shall be twice as old as my son. How old are we now ?

Form the pair of linear equations in the following problems and find their solution by substitution method : The path traced by two trains are given by equations x + 2y - 4 = 0 and 2x + 4y — 12 = 0. Will the path cross ?

Form the pair of linear equations for the foIlowing problems find their solution by substitution method: Five years hence, the age of Jacob will be three times that of his on. Five years ago, Jacob's age was seven times that of his son. What are their present ages?

Form the pair of linear equations in the following problems and find their solution by substitution method : Ten years ago, father was twelve times as old as his son and ten years hence he will be twice as old as his son will be. Find their present ages.

Form the pair of linear equations in the following problems and find their solution by substitution method : If 1 is added to each of the two numbers, their ratio becomes 1 : 2 and when 5 is subtracted from each of these, the ratio becomes 5:11. Find the numbers.

Form the pair of linear equations in the following problems and find their solution by substitution method : Find the fraction which becomes to 2/3 when the numerator is increased by 2 and equal to 4/7 when the denominator is increased by 4 .