Do you remember how to graph an equation ?
There are two of them here. Each one is a straight line on the graph. The "solution" of the pair of equations is the point where the two lines cross.
It might help you draw the graphs if you solve each equation for 'y' first.
-- The first one is y = -x - 4 .
-- The second one is y = -3x - 6 .
-- Graffum both.
-- Find the point where they cross.