Posted by Joan on .
An unknown was prepared with the concentration of 0.000520 M. A Beer's Law plot was prepared using the absorbance values from standard solutions of ASA and a line drawn through all the points passed through the origin with a slope of 1550.2 M–1. The expected absorbance and %T values for the diluted aspirin solution prepared by the student is
and , respectively.

Chemistry 
DrBob222,
A straight line is
y = mx + b
Since the line passes through the origin, b = 0 and the equation becomes y = mx.
Since you normally plot absorbance on the y axis, and concn on the x axis, the equation becomes A = m*c or A = slope*c.
You know the slope and you know c, calculate A. To fine %T remember that A = log 1/T or A = 100/%T.