Two lines are perpendicular if their slope m and m' satisfy the equation

The slope of the given line is 4, because the line is written in the slope-intercept y=mx+q, where m is the slope.
So, the perpendicular slope is

So, we want a line with slope -1/4 and passing through (-1,3). We can use the formula

for the line passing trough (a,b) with slope m:

Answer:
Read the explanation!
Step-by-step explanation:
<em>Let the "certain number" be </em>
<em>. </em>
(
is a symbol for multiplication).
<em>Create a few equations and expressions:</em>
The sum of 12 and a certain number: 
The product of 3 and the number: 
The sum of 12 and a certain number is equal to the product of 3 and the number:
= 
Solve!
12=3x-x
12=2x
x=6
I Think It Might Be Over Draft