With number 2 i have no idea how to do this. it would be very if you can show the steps

So in this case, we have to replace the known value.
y=3
y=-2x+3

3=-2x+3

Then we leave our unknown value alone.
= x

In this case, our x value would be 0.

We check it...
3=-2(0)+3
3=0+3
3=3

So y=3 x=0

For the second one we have...
y=3x+2
y=-3x-4

For this we substitute the y in any of the equation...
3x+2=-3x-4

We move the unknown values to one side and the ones without unlown values to the other side...
3x+3x=-4-2

Then we solve
6x=-6

Then we leave the unknown value alone.
x=

Then solve for x.
x= -1

Then for our y value we return to one of the original equations and substitute the x value.
y=3x+2
y=3(-1)+2
y=-3+2
y=-1

y=-3x-4
y=-3(-1)-4
y=3-4
y=-1

So in this case we got that x= -1 and y= -1

What mathematical statement is missing ? ? the answer is b