How to find the slope of the line passing through one point and has a slope?

You can do this in a number of ways, but the easiest is to plug the numbers into slope-intercept form and solve for the y-intercept (b). The formula is below with slope = m. 

y = mx+b 

After you've solved for b, but place m and b into the equation and you will have the line. 

Technically speaking, histograms are another version of bar charts, if you need to work one out then skim through google hope-o that -o!