You have a lot of questions here, try breaking them up into multiple posts and you may get more responses.
I will help with some.
<span>(x+3)=0
The solution is just -3.
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3m(m-4)=0
The two solutions are 0 and 4.
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(r-3)(r+2)=0
The two solutions are and 3 and -2.
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I hope this gets you started in the right direction.
I think it’s AC, but I may be wrong
These are linear equations that can be solved simultaneously;
5m+3n=41
3m-6n=9 (multiplying the first equation by 3 and the second by 5)
15m+9n=123
15m-30n= 45 (subtracting the two equations)
39n = 78
n = 2,
and for m, 3m = 9+6(2)
= 21
m = 7
Therefore, n=2 and m=7