Answer :

luana
[tex]5)\\-10y+18=-3(5y-7)+5y\ \ \ \ \ \ |omit\ bracket\\-10y+18=-15y+21+5y\ \ \ \ \ \ \ |unknowns\ on\ the\ left\\-10y+15y-5y=21-18\ \ \ \ \ \ \ \ \ |simplify \\0=3\\There\ is\ no\ solution.\\\\6)\\8(t+2)-3(t-4)=6(t-7)+8\\8t+16-3t+12=6t-42+8\\8t-3t-6t=-42+8-16-12\\-t=-62\\t=62[/tex]

[tex]7)\\4(5+2x)-5=3(3x+7)\\20+8x-5=9x+21\\8x-9x=21-20+5\\-x=6\\x=-6\\\\8)\\6(2x-8)+3=15\\12x-48+3=15\\12x=15+48-3\\12x=60\\x=5[/tex]
5. -10y+18=-3(5y-7)+5y
do the parenthasees first
-10y+18=-15y+21+5y
group like terms (y with y and numbers with numbers)

-10y+18=-10y+21
add 10y to both sides and you get
18=21 which is false
so no solution

6. 8(t+2)-3(t-4)=6(t-7)+8
do the parenthasees
8t+16-3t+12=6t-42+8
group like terms
5t+28=6t-36
subtract 5t from both sides
28=t-36
add 36 to both sides
64=t

7.  do the parenthasees first
20+8x-5=9x+21
add like terms
15+8x=9x+21
subtract 8x from both sids
15=x+21
subtract 21 from both sides
x=-6

8. distribute the parenthasees 
12x-48+3=15
add like terms
12x-45=15
add 45 to both sides
12x=60 
divide both sides by 12 
x=5