Well to start, we need to combine like terms all the equations together , so
n+ 4n+4n = 9n
-2-7 = -9
put them together and it’s
9n - 9
the perimeter is 45 so
9n - 9 = 45
+9 +9
——————
9n = 54
——————-
9 9
Then the 9 cancels, drop down the n and divide 54/9 and you get
n = 6
and that’s the answer
to prove it
you can do
4(6) - 2 = 22
4(6) - 7 = 17
+ 6 because you just replace the n with 6
Add them...
22+17+6 = 45
and so now we know for sure the value of n is 6!