Question 1202973
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Another approach would be to plot the function 
f(x) = 3cos(2x) - 2sin(2x) - 1
and look for the x intercepts aka roots.


I have done so with this Desmos plot
<a href="https://www.desmos.com/calculator/zeflra7phh">https://www.desmos.com/calculator/zeflra7phh</a>
The blue shaded region represents the interval {{{0 <= x <= 2pi}}} aka [0, 2pi]
2pi = 6.28 approximately


Each x intercept is labeled on the graph, and also in the left-side panel.
With Desmos, you can click on the roots to have the coordinates show up.


The four approximate solutions in that interval are: 
0.351
2.203
3.492
5.344


To confirm each solution, plug them back one at a time into f(x)
For instance, let's try x = 0.351
f(x) = 3cos(2x) - 2sin(2x) - 1
f(0.351) = 3cos(2*0.351) - 2sin(2*0.351) - 1
f(0.351) = -0.0008354950597464
There's some slight rounding error going on. But it's close enough to 0.
Make sure your calculator is in radian mode.
I'll let you check the others.
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