Use the distributive property to remove the parentheses 5(x-4)+3x-9x=6-(2x+5)+8x

start on one side by distributing 5 to (x-4) = 5x -20 + 3x-9x
then simplify: 5x-20 +12x
simplify again: 17x-20

go to your other side and distribute 6 to -(2x+5)
but now you have a negative in front of the parentheses so it’s important to distribute the negative. so now your (2x+5) becomes (-2x-5)

so when you distribute the 6, it becomes -12x-30+8x.
simplify like you did the other side: -4x-30
and set the first side:17x-20 equal to -4x-30

so it should look like this: 17x-20 = -4x-30 now you can simplify the entire equation by adding -4x to both sides:
21x-20=30

add 20 to both sides

21x=50

x= 2.38 which is equivalent to 2.4

if you plug that back in you should find that 21 • 2.4 ≈ 50.4 or 50 :)