Step-by-step explanation:
the lines are all going through the origin (0, 0), so the y-intercept is the same (0) for all 4.
therefore, we only need to focus on the slope of the lines to see which two are identical.
the slope is the ratio "y coordinate change / x coordinate change" when going from one point to another on the line.
one point is for all 4 lines the origin, so the coordinate changes are the point coordinates themselves, and we only need to calculate y/x and see, which ones are equal.
105/15 = 7/1 = 7
150/12 = 50/4 = 25/2 = 12.5
120/10 = 12
96/8 = 12
so, C and D have identical slopes and therefore identical graphs, and have therefore the same costs of T-shirts.
