Multiply the -3 with the stuff in the ( ) and you get -3x+15 since a negative and a negative equal a positive the 15 is positive so now you have -3x+15+4x =24 now you add like terms and you have 1x+15=24 then -15 from both sides so 15-(-15) cancels out then 24-15=9 then you have 1x=9 divide the 1x end the answer is x=9