Because you're trying to make them congruent, equal the two expressions to each other.
So, for #10 you would equal them so it would look like this.
2x+2=5x-19
Then you would just go ahead and simplify
2x+2=5x-19
-2x -2x
---------------
2= 3x -19
+19 +19
---------------
21=3x
--- ----
3 3
x=7
This means that x should be 7. You can check this just by plugging it in
2x+2
2(7)+2 = 16
5x-19
5(7)-19= 16
Same with #11.
x+8=3x-14
-x -x
--------------
8=2x-14
+14 +14
--------------
22=2x
--- ----
2 2
x=11
Check.
x+8
11+8= 19
3x-14
3(11) - 14 = 19
