Question 10424
This is a simple matter of substituting the given values of x or y and solving the equation for the other variable.

1) y = 2x + 7

(a)Given (0, ?), substitute x = 0 into the equation and solve for y.

 y = 2(0) + 7
 y = 7

The ordered pair for (a) is : (0, 7)

(b) Given (4, ?), substitute x = 4 into the equation and solve for y.

y = 2(4) + 7
y = 8 + 7
y = 15

The ordered pair for (b) is: (4, 15)  Get the idea?

I'll do (a) of the second problem, then you try (b).

2) 3x - 7y = 30
(a) Given (3, ?), substitute x = 3 into the equation and solve for y.

3(3) - 7y = 30
9 - 7y = 30  Subtract 9 from both sides.
-7y = 21 Divide both sides by -7
y = -3

The ordered pair for (a) is: (3, -3)

Try (b), but in this one, you are given the y-coordinate (3) and you are to solve for x. Otherwise, the procedure is the same.