Form the pair of linear equations for the following problems and find their solution by substitution method.

Five years hence, the age of Jacob will be three times that of his son. Five years ago, Jacob’s age was seven times that of his son. What are their present ages?

Solve the following pair of linear equations by the elimination method and the substitution method :

3x + 4y = 10 and 2x - 2y = 2

Solve the following pair of linear equations by the elimination method and the substitution method :

3x - 5y - 4 = 0 and 9x = 2y + 7