let's build on your basics a bit. read through my answer here

https://thebasicanswers.com/1337/rate-law-from-concentration-vs-time-data

note this table of equations

.. .. .order.. .. .. . non-integrated.. .. .. . ..integrated

.. .. . .. 0.. . .. . ...rate = k x [A]°... .. .. . . ..[At] = -kt + [Ao]

.. . .. .. 1.. . .. . ...rate = k x [A]¹... .. .. . . ln[At] = -kt + ln[Ao]

.. . .. . .2... . .. .. .rate = k x [A]²... .. .. . . 1/[At] = +kt + 1/[Ao]

note the difference between non-integrated and integrated

.. non-integrated... RATE vs concentration

.. .. . .integrated... .TIME vs concentration

and from calculus, we know that the derivative of a function at a given point = the tangent at that point on the curve. and we can see that the non-integrated rate law is the derivative of the integrated curve.

meaning...

.. the rate of reaction = the slope of the tangent line at the given t value on the

.. time vs concentration plot.

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so.. do this

.. (1) draw the plot

.. (2) draw the tangent line

.. (3) pick two points on the tangent line and calculate slope.

.. .. ..I chose (20,0.42) and (60,0.28)

.. (4) rate = -1 * that slope... (it's negative because -d[A] / dt = rate... it's decreasing)

***********

I get

.. rate = - (0.42 - 0.28) / (0.20 - 0.60) = 0.0035 M/sec