use the FOIL technique (first outer inner last) to solve this.
FIRST: multiply the x and the 5x to get 5x^2
OUTSIDE: multiply the -4 and the x to get -4x
INNER: multiply the -6 and the 5x to get -30x
LAST: multiply the -4 and the -6 to get 24.
last step: put it all together to get 5x^2 - 4x - 30x + 24, which is 5x^2 - 34x + 24.
