The independent variable of an equation is x, or something u can change. in linear equations, for example, it is y=3x+4. and x is the independent variable cause most of the time u will plug in or substitute a number for x.
Solution :
a).
Given : Number of times, n = 25
Sigma, σ = 0.200 kg
Weight, μ = 13 kg
Therefore the hypothesis should be tested are :


b). When the value of 
Test statics :



= 45.5
P-value = 2 x P(Z > 45.5)
= 2 x 1 -P (Z < 45.5) = 0
Reject the null hypothesis if P value < α = 0.01 level of significance.
So reject the null hypothesis.
Therefore, we conclude that the true mean measured weight differs from 13 kg.
I think the problem is
2X+20=400
You just have to answer I think X and X equals that two numbers I’m not 100% sure but I’m trying to help