The value of f(5) is 
Step-by-step explanation:
The function is 
To find
substitute
in 

Multiplying the terms, we get,

Adding the terms, we get,

Thus, the value of
is 
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
Hey there!
BOD is a 90 degrees angle. Make an equation for that angle. 15+12+x=90. Simplify this to 27+x=90. You need to isolate x, so subtract 27 on each side to get x=63. C is the answer.
I hope this helps!