Process of elimination:

Multiply equation 2 by 3 to get the same coefficent in front of x: 3x - 3y = 9 (3)

Subtract eq 3 from eq 1 to get: y = 3

Substitutute our value for y into eq 2 for simplicity: x - 3 = 3 therefore x = 6

Process of substitution: Add y to the right hand side of equation 2 to get: x = 3 + y

Substitute this expression of x into equation 1 to eliminate x: 3(3+y) - 2y = 12

Expand and simplify: 9 + y = 12 therefore y = 3

Substitute this value of y into equation 2 and solve for x: x - 3 = 3 so x = 6

Factorise x^2 - 14x + 49