Mia's work to find the slope of a trend line through the points (3, 10) and (35, 91) is shown below. Mia's Work Step 1 StartFraction 3 minus 35 Over 10 minus 91 EndFraction Step 2 StartFraction negative 32 Over negative 81 EndFraction Step 3 StartFraction 32 Over 81 EndFraction What was the first error that Mia made?