1. The distance between the focus of the linear function and the Y axis and the X axis is 4, that is, when x=0, y=b=4.

So the resolution function is y=2x+4.

2. Simultaneous y=4-3x and y=2x- 1, and the solutions are: x= 1, y= 1, so the intersection point is (1, 1).

And y=ax+7 passes through the intersection of linear functions y=4-3x and y=2x- 1,

So 1=a+7,

So a=-6

3. Let the proportional function be y=kx and the proportional resolution function be y=4/3x, because it passes through point (3,4).

Let the linear function be y=kx+b, that is, the intersection with the y axis is b.

S=3*b/2= 15/2 (it should be the absolute value of b, which is difficult to express).

So b=5 or -5.

And because the function passes through points (3, 4),

So k=3, b=-5 or k=- 1/3, b=5.

That is, the main resolution function is y=3x-5 or y=- 1/3x+5.