The first day of junior high school, The following equations are solved by the method of introduction y=x+3 3s—t=5 3x+4y=16 4〔x-y-1〕=3〔1-y〕-2 7x + 5Y = 9 5S + 2T = 15 5x-6y = 33 / 2 x + 3 / 3 y = 2

The first day of junior high school, The following equations are solved by the method of introduction y=x+3 3s—t=5 3x+4y=16 4〔x-y-1〕=3〔1-y〕-2 7x + 5Y = 9 5S + 2T = 15 5x-6y = 33 / 2 x + 3 / 3 y = 2

(1) Y = x + 3 (1) 7x + 5Y = 9 (2) substituting formula (1) into formula (2) 7x + 5 (x + 3) = 97x + 5x + 15 = 912x = - 6x = - 1 / 2 into formula (1) y = - 1 / 2 + 3 = 5 / 2  x = - 1 / 2; y = 5 / 2 (2) 3s-t = 5 (1) 5S + 2T = 15 (2) substituting formula (1) t = 3S