(i) 2x + y = 7

y = 7 – 2x

Put x = 0,

y = 7 – 2 * 0

y = 7

(0, 7) is the solution of the equation

Now,

Put x = 1

y = 7 – 2 * 1

y = 5

(1, 5) is the solution of the equation

Now,

Put x = 2

y = 7 – 2 * 2

y = 3

(2, 3) is the solution of the equation

Now,

Put x = -1

y = 7 – 2 * - 1

y = 9

(-1, 9) is the solution of the equation

The four solutions of the equation 2x + y = 7 are:

(0, 7),

(1, 5),

(2, 3)

and (-1, 9)

(ii) πx + y = 9

y = 9 – πx

Now,

Put x = 0

y = 9 – π * 0

y = 9

(0, 9) is the solution of the equation

Now,

Put x = 1

y = 9 – π * 1

y = 9 - π

(1, 9 - π) is the solution of the equation

Now,

Put x = 2

y = 9 – π * 2

y = 9 – 2 π

(2, 9 - 2 π) is the solution of the equation

Now,

Put x = -1

y = 9 – π * 1

y = 9 + π

(-1, 9 + π) is the solution of the equation

The four solutions of the equation πx + y = 9 are:

(0, 9),

(1, 9 – π),

(2, 9 - 2 π)

and (-1, 9 + π)

(iii) x = 4y

Now,

Put x = 0

0 = 4y

y = 0

(0, 0) is the solution of the equation

Now,

put x = 1

1 = 4y

y = 1/4

(1, 1/4) is the solution of the equation

Now,

Put x = 4

4 = 4y

y = 1

(4, 1) is the solution of the equation

Now,

Put x = 8

8 = 4y

y = 2

(8, 2) is the solution of the equation

The four solutions of the equation πx + y = 9 are:

(0, 0),

(1, 1/4),

(4, 1),

and (8, 2)