Answer:
This is how you would work it out...
3x-8x-5=10
3x-8x=10+5
-5x=15
X=-3
The mistake is that they did 8-3 not 3-8. Answer should be with a minus... x=-3
-3(2x-3)=33
-6x-9=33
-6x=33+9
-6x=42
X=-7
The mistake is how they expanded the bracket also the fraction (it is irrelevant). Answer is x=-7