Question

Alex was finding the average change of his stocks over the following months: -10.29 in June, -8.16 in July, 34.50 in August, 3.12 in September. Estimate the average change in his stocks by rounding first to the nearest whole number and then dividing by the number of months.

Answer 1

Pretty much asking you to estimate the difference quotient:
\[\frac{f(x+h)-f(x)}{h}\]
June to July:
\[\frac{f(7)-f(6)}{7-6} \approx \frac{10-(-8)}{1} \approx 18\]
Follow similar steps for June to August, July to August

Answer 2

and september