I know this probably is not what you are looking for, but this is what I would suggest.
Write down on the side what values they are giving you and the corresponding variable used for that value.
Like for the first question, they give you mass is 3000kg.
On the side write
m = 3000kg
m is the variable used for mass
Then list any other variables they give you in the question and then what you are trying to look for.
a = 2m/s^2
F = ?
a is the variable for acceleration and F is the variable for force.
So now you have:
m = 3000kg
a = 2m/s^2
F = ?
You have a and m, and you are looking for F (force), you know that because it asks "with what force".
Also note, that you have to know what the variable is based on the units and you likely have some type of formula sheet with all of them listed.
You can use the variables and what is unknown to match it to a formula that will solve for the unknown variables. Also note, that it might not always be simply a=b+c, you may know what "a" and "b" are, but they may ask for c so you will have to rearrange the formula with some simple algebra.
This question however is simple. You can see you are going to use the formula
F=ma.
So now just substitute in your variables to solve for F.
(3000kg)(2m/s^2) = 6000N
<u>Make sure to write the units</u> which are probably on your formula sheet as well. Force is measured in Newtons, so you use the unit N.
Also note, if they gave you mass in grams (another unit), you cannot use that in the formula (your formula sheet would tell you the unit it must be in), so you would have to convert it to kg.
Hope this helps as a starting point. I don't intend to do your homework for you, but explain a process you can use to help you do it on your own.