Hi
1. What does the error say? "The expression to the left of the equals sign is not a valid target for an assignment."
This is referring to eq5 = eq4 = eq3 etc... Matlab does not understand what you want to do in this line
2. I think you misunderstood how solve works. You need to actually pass it equations, and add the variables of interest at the end.
eq1 = 1.2962e+04*(0.127-x1);
is not an equation. This is a variable eq1 with the value 1.2962e+04*(0.127-x1). So, you would need to do something like
sol = solve(eq1==eq2, ... , x1,x2,x3)
3. Last but not least, I think there is a typo in your code, some of the constants do not match the original equations you gave
