how i calculate the equations of straight lines

For  calculating  the equations of straight lines  we  need to be given data in one of the following forms
(i) Point slope form : a point on the line and its slope is given   then the equation of line is given by 
(y-y1)=m(x-x1)

(ii) Two point form:  when two points on the line are given(y-y1)=(y2-y1)(x-x1)/(x2-x1)

(iii)slope intercept form: slope and intercept is given

y-c=m(x-0)

(iv) intercept form: when intercepts on the axes are given so x/a+y/b =1

(v) normal form

So depending what sort of data is given you can find the equation of line