Combined Dependent Variable Interpretation

#1
Hi,
I am running a regression model with a dependent variable called "pollution" which is based on an average of five variables. How should I go about interpreting results and the coefficients from my regression model?
I have two independent variables in my regression model that are both very significant.

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#3
The regression coefficient of X is the expected increase in the dependent variable for a 1-unit increase in X with all other independent variables in the model held constant.