Using the results of the previous task, compose the equation and find its sides knowing that the perimeter

Using the results of the previous task, compose the equation and find its sides knowing that the perimeter of the triangle ABC is 19 cm.

To find the sides of the triangle, we solve the equation, define the variable x, and then we can count the sides of the triangle ABC.
P (ABC) = 19 cm;
3x + 7 = 19;
3x = 19 – 7;
3x = 12;
x = 12: 3;
x = 4.
AB = x = 4 cm;
BC = x + 5 = 4 + 5 = 9 cm;
AC = x + 5 – 3 = 4 + 5 – 3 = 6 cm.
Answer: AB = 4 cm; BC = 9 cm; AC = 6 cm.