The equations are: 1, substitution elimination method, 2, addition and subtraction elimination method, 3, gauss elimination and so on.

Addition, subtraction and elimination method is suitable for solving the equation with the same unknown coefficient as integer multiple, such as

x

+

y

=

nine

................& lt 1 & gt；

x

-

2y

=

-3..............& lt2 & gt

& lt 1 & gt；

-

& lt 1 & gt； get

3y

=

12

y

=

four

X can be obtained simply by substitution.

=

five

3x

-

y

=

1..........................& lt 1 & gt；

2x

+

3y

=

8.....................,.& lt2 & gt

Observation shows that the coefficient of y is three times, so

3×& lt； 1 & gt；

+

& lt2> gets

1 1x

=

1 1

x

=

1

Then y is obtained by substitution method.

=

2