Lila wrote an equation of the cost for printing brochures, where x represents the number of brochures and y represents the total cost. The total cost for 35 brochures is $41.45. The total cost for 65 brochures is $55.55. Step 1: Write the ordered pairs (35, 41.45) and (65, 55.55).

Step 2: Find the slope. m = StartFraction 55.55 minus 41.45 Over 65 minus 35 EndFraction = 0.47

Step 3: Find the y-intercept to write the equation in slope intercept form. y minus 55.55 = 0.47 (x minus 35). Y minus 55.55 = 0.47 x minus 16.45. y = 0.47 x + 39.1.

Which explains the error that Lila made?

Lila made an error in Step 3 when she did not use the x- and y-coordinates from the same ordered pair.