As it is used in the first stanza of the poem below, the word trod most nearly means:

The slope of a linear equation is equal to the change in the value of the dependent variable divided by the change in the value of the independent variable. in this problem, the dependent variable is the profit while the independent variable is the worker's average pay. if the profit is said to increase by 1500 when worker's average pay decrease by 450, the slope is equal to 1500/(-450)=-3.33