I need help in math
If you have x and the corresponding y values, then you can plot the straight line on a graph paper. Y axis being the vertical axis and X axis being the horizontal axis. Once your x and y values are plotted, draw the best fit line that passes through most of the points. Extend the straight line till it cuts the y-axis and the y-intercept is the b value.
Is by calculations. If you have 2 sets of x and y values, do simultaneous equations and you can get both 'm' and 'b' values.