The table shows the low outside temperatures for monday, tuesday, and wednesday.

see attachment

by how many degrees did the low temperature increase from monday to tuesday?
this function table shows the outside temperature for a given day

a. 7.7⁰

b. 8.7⁰

c. 8.8⁰

d. 25.3⁰

-8.8 - (16.5) =
-8.8 + 16.5 =
7.7 <==

The method for doing this will depend on the required accuracy of your estimate.

Using linear approximation between 9^2 = 81 and 10^2 = 100, the estimate is
.. 9 +(90-81)/(100-81) = 9 +9/19 ≈ 9.47

Using one round of "Babylonian Method" on the above estimate,
.. (9.47 +90/9.47)/2 ≈ 9.486 ≈ 9.49 . . . . . . actually accurate to the hundredths place

Using derivatives and linear approximation,
.. √90 ≈ √81 +1/(2√81)*(90-81) = 9.50
or
.. √90 ≈ √100 +1/(2√100)*(90 -100) = 9.50