Expand and simplify (x − 4)(2x + 3y)^2

First concentrate on expanding the squared term, don't try and do it all in your head, the 2x+3y term should expand to give 4 separate terms. Then combine any terms with the same configuration of x and y, in this example there will be two terms ending "xy". After expanding the 2x+3y term multiply the values with the x-4 term and again combine terms with the same x y configuration.