First, let's explain the variables. F means force, m means mass, and a means acceleration. F is measured in Newotns [N], mass is measured in kilograms [kg], and acceleration in measured in meters per squared second [m/s²].
Now let's mover on the first problem.
Given
m = 1000 kg
a = 3 m/s²
According to the second law of Newton, the force is equal to the acceleration multiplied by the mass.
The answer is 3000 N.
The second problem is smiliar.
Given
m = 70 kg
F = 250 N
We use the same formula from before, and use a bit of algebra to adapat it to our needs.
The answer is 24 1/7 s/m^2.