Astudent collected the following data for a fixed volume of gas:
temperature (⁰c) pressure (mm of hg)
10 726
20 750
40 800
70 880
100 960
150
fill in the missing data point. show all calculations leading to an answer.

First, you should convert the temperature unit to absolute temperature.

Second, you shoul graph the points. Then you will find a pretty linear correlations among the points.

You can pick between using the best fit line or you could observe that as you get to  higher temperatures the linear behavior is "more perfect".

I found this best fit line:

P = 2.608T + 14 
Then, for T = 423K

P = 2.608(423) + 14 = 1117 mmHg

If you prefer to use the last two points, this is the calculus:

[P - P1] / [T - T1] = [P2 - P1] / [T2 - T1]

[P - 960]/[423 -373]   = [960 - 880] / [373- 343]

=> P = 1093.3 mmHg.

You can pick any of the results 1177 mmHg or 1093 mmHg, You need more insight to choose one of them: conditions and error of the experiment for example.