From 1st eqn x=7y-47. Substitute for x in 2nd eqn: -6(7y-47)-8y=-18; -42y+282-8y=-18; 282-50y=-18; 282+18=50y; 300=50y so, dividing through by 50, y=6. Therefore, x=7*6-47=42-47=-5.
Check out the result by substituting x and values in each original equation: -5-42=-47; 30-48=-18. Right!