81- answer is ok but im not suree
Answer:
X= - 44
18x+3x+4-5=5(4x9
Collect like terms
21x+4-5=5(4x-9
More variable to the left hand side and change its sign
21x-20x-1=-45
Correct like terms
X=-45+1
Which is x=-44
I think n is 9 hope i helped
It probably gos like this here's my answer for number 1 6/8 and 9/12. for number 3, 10/12 and 15/18.