The solution is x < 3.
Solution:
The given expression is 3x + 4 < 13.
To solve the given inequality.
3x + 4 < 13
Subtract 4 tiles on both sides of the inequality.
⇒ 3x + 4 – 4 < 13 – 4
⇒ 3x < 9
Divide by 3 tiles on both sides of the inequality.
⇒ 
⇒ x < 3
Hence the solution is x < 3.
The answer is 4 isn’t it?
Perimeter is the sum of all sides in the figure. Here, all six sides are equal in length so it would be:
p = 6 * side
p = 6 * 3.9
p = 23.4 cm
In short, Your Answer would be: 23.4 cm
Hope this helps!