Explanation:
A. When we are given two points we can find a linear equation by finding slope of the line and substituting it in point-slope form of equations.
Let (0,0) and (3,6) be two data points. Now we will find slope from these points.


Now we will substitute our values in point-slope form of linear equations.





Therefore, our resulted linear equation will be

B. We will substitute the rate of change (slope) and initial value (y-intercept) into slope-intercept form of line to get the desired equation.
Let 4 be our initial value and -2 be our rate of change then,

Substituting x=0 we will get value for b that is our y-intercept.


Therefore, our equation for line will be
.